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Heat is a function of work. The same motor making 300hp can be working a lot harder than another. So you want to be efficient.
Now everything is a compromise. A really efficient setup for track isn't going to be as ideal for the street, and vice versa.
Once you know the power you want, look at compressor maps. Find a turbo that will be as efficient as possible in the revs seen at the track. That's doesn't mean at redline, track rev range is 5500-7500. So the one that shows the best average comp efficiency in that range, for the power you want. Then pick a turbine housing that can efficiently flow that power.
Both these aspects contribute to better VE. Cooler air, cooler EGT.
Some people say pick the smallest turbo that get reach a target hp. And that's an understandable method for a street only car, as it will give the earliest spool up.
But on the track, you are using 5500-7500; so do you really care if the turbo spools a few hundred rpm later because you chose the larger turbine housing?
That was my methodology anyway. I only want 280-300whp. I could've gone with a gtx2860r, gtx2863r, gtx2867r, gtx3071r, gtx3076r.
All turbos could achieve the power. When I plotted the comp maps, the gtx2867r had the highest average comp efficiency in the rev range, target power, and estimated boost. The two smaller ones were getting too far beyond their peak efficiency islands. The two larger ones were not getting into their ideal efficiency islands. The two larger ones would still have been okay, and also provided more head room if wanting 350whp, which changed everything and made them the better choice.
Then looked at turbine map and a 0.63 a/r is getting near choke at the level I was chasing (so obviously not efficient) so I went with the 0.86.
So I could've gone with a gtx2860r 0.63, which would have made for a lightening quick spool setup, but it would gotten inefficient at the rev range I wanted to rape it in. I also could have gone the other end and gone gtx3076r 0.86, but it offered no more comp efficiency at my level, and I didn't need a gt30 frame 0.86 turbine housing. I could've gone 0.63 housing on the gtx3076r, but that pretty much flows the same as a 0.86 gt28; so I don't gain any efficiency, but lose response and gain lag as now I have bigger wheels to move.
If you want to so the homework (and learn to do it yourself) the info is out there to do so. The key is to be realistic.
Asking broad questions on forums such as you have, is only ever going to result in "I have this kit and it's good" More often than not, these opinions are subconscious self justification bias, and realistically, most will blindly back their own choice, and have not actually tried anything else; and often have just bought their kit from an ad, or another persons review saying that it's awesome.
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