bolt on vs t3 3076

[cam1391]

Im about to start placing orders for my BT build. I was pretty dead set on an ATP iwg gtx3076r (iwg bracketed shut) with a CP-e 44mm ewg stock flanged manifold. This seems to be plenty capable of getting me to my goal of close to 400whp with supporting mods on stock internals, and my ultimate goal of 450-475 whp @ >400wtq once I get the scratch together for the weisco pistons/manley h-beams, balanced oem crank, ballance shaft delete, etc.
But about half the people I talk to say I should "do it right" and go t3. Is there really any significant reason to with the ultimate goal im looking to get to other than faster spool? Which im not trying to have full spool till around 4k rpm anyway to preserve my engine from a rod taking a scenic tour of my block.
If I were to go t3 im pretty sure id still go gtx3076r (not sure what ar size though, probably .78) with a steedspeed cast top mount (if I can even actually find one) t3 twin scroll manifold.
I guess my real question is if its sooo much better to go t3, how come almost everyone goes atp, especially at the same price point?
P.S. either way ill be going with a Treadstone TR8 fmic with HTP's new bottom rout (under the engine)intercooler piping kit! I HIGHLY SUGGEST you check it out if you havent already seen/heard, its not on their website yet but theres a thread here on msf. They also have a k04 wastegate actuator adapter bracket so you can spin the compressor housing to point downward for those wanting to run it with the stock turbo. Obviously im stoked!
As always, I appreciate the input.