You should get a Tri bike, if you‘d like to do tris. Otherwise buy a TT bike (not every brand has both options). You wont need all these storing and hydration options.
Buy the TT if you want to get faster and
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if you already have a well fitting aero helmet
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if you already have a very well fitting aero suit
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if you are willing to spend time and money to find a very good position on the bike (if not, chances are high, that you won’t be faster, because you can’t produce the same watts, you can’t hold your position or you are simply not aero enough)
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if you are willing to train in this position A LOT to really be faster than with your road bike
Otherwise the TT bike wont make you faster or there are cheaper options to get faster.
Also consider that riding a TT bike on the road is more dangerous (out of competition) and you will see less of the beautiful scenery around you.
But: If all this doesn’t bother you, riding a well fitting TT is like the felt difference in speed between a MTB and a Roadbike. It just feels awesome!