60mm is way too little. I’d suggest the distance from your foot on the pedal to the ground as a practical minimum (for stoplights/road crossings), which is probably 125mm. I tried a 75mm that was stock on a Specialized Epic, and it was a complete joke. I put a 75mm on my kids bike and it’s still a complete joke.
They’re all the same for the most part. Go to a bike shop and try one there. I’d recommend the Fox/Raceface SL (Raceface is usually on sale) as it has the lightest dropping action if you don’t need to ever have it at less than all up. If you want infinite adjustment, the OneUp V3 or BikeYolk Devine are the way to fly.
The added weight is pretty minor to the potential benefits if the course is more technical. Knowing the course can help make your decision. If there is very little technical parts of the course you can probably get away without it.
On unknown courses it can be really helpful for those “ohh crap” moments when you don’t/didn’t know that feature was much bigger than you thought it was. Much easier to manage those when the seat is down and out of the way.
Fatigue: I have no real proof, but dropping the post and negotiating obstacles can be easier/less fatiguing than getting your butt back behind the seat and pulling yourself back up. I have done a long day with a dropper that didn’t work and it took more effort over the rocky chunky bits. It would have been really nice if it worked since my brakes didn’t.
As mentioned before if you are not going to use it don’t put it on. I spent 4 days of racing stuck behind many people not putting their post down when they should have them down. Even worse is that they were barely getting behind the saddle.
