I know it's not me, but i also have experience in both... the supra is a small pretty car, but it feels too small for me, I'm 6'1 250 lbs... the mustang is much more roomy and comfortable.
The A10 is crazy fast, almost like a cheat code... fbo e85 will have no problem pushing 500 whp and being able to keep up with a stock gtr from a dig and from a roll... and you cab go balls deep and the stock engine/trans will handle 900 whp without a blink...
Particularly, I'm not a big fan of the Whipple... too much torque down low, the "holy shit" factor is there because it's a lot of torque... but with a lot of torque comes a lot of spinning... you will need to run m/t ss in the back on a fat size and still it will break loose. I like more of a linear powerband like the ess supercharger.
Either way, any brand name suspercharger (paxton, Whipple, ess, vmp, etc) will give you good results and you can always upgrade the systems with minor stuff... a stage 1 (basic kit) will be good for around 600 whp... bap and injectors will be high 600 low 700.. return system and e85 will push +800 whp... and pulley down is super easy... gen 2 engines (15-17) can handle more boost than the +18 due to the lower compression, but +18 come with the A10 vs the A6, and that transmission is no joke... the difference between the A10 with drag mode vs a manual car, feels like you need f/i just to keep up
Also... there is nothing like the "gtr tax"... you can get a basic s/c setup brand new for under $5k
New bmw engines handle boost pretty good too, and supras move pretty decent with minor bolts and also have a good trans... i have a friend with a 135i N54 with about $3k on it and the little turd pushes like 550 whp and weight nothing... but at the end of the day, you have all the bmw gremlins