Very rarely is there a lengthy AND steep uphill finish to where w/kg is even a factor. W/kg is a nice metric to obsess over and give a general idea of fitness, but when it comes down to results, absolute power is king simply because every race isn’t a mountain top finish.
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unfortunately for us lighter built riders this is true! Fortunately we can still have good kick and/or a low CDA
I’m not so sure about that. My experience was that unless I could get my FTP up to 4.5 W/kg, I would either A) get popped or B) couldn’t really muster much of a sprint at the end of a race, flat or not. This was racing against national calibre riders in our A grade, mind you.
I don’t think either of you are necessarily wrong or mutually contradictory. Consider - you’re comparing national elite riders against what would be quite a few rungs down - at least in my case. Also, 4.5 watt/kg likely involves quite a few raw watts, even if you’re feather light. Consider a 160 lb rider (72.6 kg). At 4.5 watt/kg, that person’s FTP is 326 - right around my 336 FTP. If we’re on relatively flat terrain, we’re likely to be fairly evenly matched and most amateur courses (at least where I live) don’t have any climbs longer than 2-3 minutes.
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Where are you from @cerb sounds familiar. The climbers come out for the climbing races. Flat land riders and roulers come out for all other races.
Melbourne! Pretty sure this will happen most places though… 
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W/kg only tells you how fast you can climb on a sustained, steep gradient. In of itself, it does not mean anything when it comes to the flat or short climbs (ie a couple minutes MAX). Raw, absolute power does (to a point, then CdA becomes a factor). Not sure about you, but not many races over here end in a 10+ minute steep climb.
Now, I don’t doubt that 4.5 w/kg really meant that for you, but moreso that having that level of fitness came with all the other ancillary aspects of riding fitness–your sprint power, short burst repeatability, and most importantly, an overall higher FTP.
Take for example:
Rider A: 247.5 FTP, 55kgs
Rider B: 360 FTP, 80 kgs.
Same w/kg, which ultimately means they stand a fair shot neck and neck on the same, steep gradient, however Rider B is more equipped to get better results overall on any course sheerly because of the higher raw power.
To your example, the reality of the difference in my experience is that plenty of the riders I ride against who are 60kg, will still have a threshold of 300W+. This means that the small guys can still ride tactically against the big guys on the flat courses (most of the larger guys will be 350+ FTP), but with their FTP at 5W/kg they destroy the bigger guys any time the road rises.
For me to have a 5W/kg threshold, i’d need to do 440W. That’s pro level numbers. The best large local guys I race against ‘only’ have around 400W FTP’s.
However, plenty of smaller riders in the range of 60-70kg have FTP’s in the range 300-350W - making 4.5-5.0W/kg+ sustained climbing power a requirement to hang.
Further, if the hills are short efforts and you’re doing 6.5W/kg for 2-3mins, thats 550W+ for me, but only <400W for the small guys. This means that I have to work at 1.7x threshold, while the smaller guys work at only 1.3x threshold for the same effort. That makes it more sustainable AND repeatable for the small guys.
Once you reach a certain point, it is difficult to get more RAW power. For most locally competetive cyclists, a threshold above 400W will be near impossible. However, a threshold of 300-330W is within grasp of most ‘high level local athletes’, (almost) irrespective of size.
Based on this, I feel that it is difficult to be a top level ‘local athlete’ if you are over 80kg - as 5W/kg requires 400W threshold at this weight. Tactics always come into play in racing, but the physiological numbers are really against you at that point.
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I’d be interested for some input on how much watt/kg affects cyclocross racing.
On one hand…it’s unusual(at least around here) to have any kind of real, sustained climbs.
On the other hand…there are a lot of accelerations out of corners and obstacles. And also I have to imagine more weight would leave one more susceptible to losing watts to bumps in the course…more mass jiggling around over the bumps.
Also…I have to believe less weight makes cornering easier as well.
Then on the OTHER other hand…higher rolling resistance is often looked at as a static loss of watts…which should favor the larger, higher absolute wattage rider.
I remain confused 
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Definitely pros and cons in CX. Look at top Pros
WVA and MVDP are both pretty large units, against upcoming smaller riders who also do well like Iserbyt and Pidcock, along with everything in between!
Your perspective is inline with my own experience. I’m that annoying 64kg rider with the 310+w FTP, depending on the time of the season. Like you said, it’s not difficult for me to draft strategically no matter who is drilling it at the front, and then once the road turns up, it’s a different math equation. Even on our Tuesday night worlds with a 5 min climb, it’s pretty rare to see someone in the front group over 175 pounds for the reasons you mention.
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I think lighter riders do have a bit of an advantage with accelerations, but it definitely depends on the course.
I’m right around 4.5 w/kg with a 285 watt threshold, so about 140 lbs. I definitely notice that I seem to be able to out accelerate guys I’m racing against fairly easily, but once we get up to speed I start to fall off. Generally, the more stop and go corners there are the better. On courses where the effort is very steady, I suffer. I also notice I’m decently good at getting hole shots if I start on the front row.
Cat 2 / B Grade
4.2 w/kg FTP 342
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That’s generally my experience, on the same courses I believe (chicrosscup). Well opposite actually…I’ve got a similar ftp, but I,ve got 40 pounds on you. Keeping up with the group out of corners is tough, but I tend to put distance on people when there are sustained power sections.
Of course I’m a bit farther back in the field lol 
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This will be my second season racing so I am CAT 4 at ~3.9W/kg.
FTP: 330
Weight: ~188 lb
Recently moved to a much flatter area so I’m hoping that helps at my weight
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Ha, yeah I just lurked your crossresults we’ve raced each other a handful of times.
It’s interesting and kind of shows this thread is really silly.
There’s such a huge range of w/kg in every category and individual results are really more dependent on a combination of power, race craft, and course selection as opposed to outright power.
There’s guys with higher w/kg than me in lower categories and guys with lower w/kg in higher categories!
Currently Cat3 with a 4.1w/kg at about 72kg. Thankfully a Super high w/kg isn’t needed to be competitive in flat Florida.
Well, yes and no.
I think barring really unusual circumstances, like a purely downhill race, there are always absolutes…like:
-more power available is always better
-less weight is always better
-better handling skills is always better
-more stamina/repeatability is always better
It gets interesting though when one strength can cover up for obvious deficiencies…like the 220lb jiggly guy who just blows past people, or someone with a low power profile that just effortlessly cruises through corners at speed.
Anyway, good luck, and see you in the fall. With any luck I’ll cat up and see you in some of the 3 races.
It also becomes more complicated when one of those absolutes comes at the expense of another. Like losing weight leading to lost power.
That gives me some hope… I’m not likely to start road racing regularly, but it would be fun to jump into some of the Intellegensia Cup races next year. Lord knows I’ll have plenty of vacation to use next summer. I love CX and haven’t had good enough results to be forced up but with that kind of road week, I feel like I have to take advantage of it at some point.
190cm, 87.5-89kg, 297 so 3.4 right now, but I’ve been both lighter in the past, and at least 15-20 watts stronger, so with some consistency (in training and diet) I should be able to get to 3.8 before next summer… maybe the standard goal of 4.0 w/kg.