The Supra is hands down a better performance vehicle. To begin with, it is RWD, vs FWD for the Celica. Also if you compare the top of the line Supra vs. the top of hte line Celica, it would be like comparing a Corvette to a Cavalier, they are just not in the same league. The Celica is a sporty looking, peppy, economical FWD car. I like the looks of the Celica, and it is a pretty good car, but performance-wise the Supra is in a whole other class.
The fastest Celica in straightline performance would be the 2000-2005 GTS model, which travels from 0-60 mph in 7.2 seconds in manual form. This is much slower than both the turbo (6.9 seconds)and twin turbocharged Supra (5.1 seconds) , but slightly faster than the older naturally aspirated Supra (the 86 does it in 8.8 seconds).
But even the slower Supra will still handle better than the faster Celica due to its RWD setup.
PS- The 1st person to answer said that the SUpra is just a souped up version of the Celica.. Although it was originally based on the Celica, by 86 it became its own class of car, and is totally different.
And to answer your question as to what year to get, the late 90's twin turbo version is the most highyl sought after version because of the twin turbo motor, and more sporty look, but you will pay a premium for this car. To find one in good condition expect to pay around $20,000. Modified versions are even more, some selling upwards of $100,000!!
Hope this helps.