it depends on what you want to do (what type of racing and what type of daily driving). since there's already a lot of posts for the supra, i'll post a little about dsms.
dsms are good cars. you can get an all wheel dsm into the 12s cheaper then you can get a supra there. first gens aren't really prone to crank walk. but hey, my buddy has a 2nd gen talon with 400 ponies under the hood and he hasn't encountered crank walk yet (2 years now). the 4g63t is a great motor. you can probably find more places for performance parts with a dsm than a supra. the turbos are built better than our ct-26. their intercoolers perform better than ours.
what type of dsm are you looking at/leaning towards? mitsubishi eclipse (1990-1999), eagle talon (1990-1998), or plymouth laser (1990-1994). Eclipse has fw turbo (gs-t) and all wheel turbo (gsx), all talons, i believe, are all wheel (turbo=tsi and na=esi), and the laser i don't really know.
every car needs maintenance. when one doesn't maintain a car, it's prone to breakdown. good maintenance = good running vehicle. if you are going to get a turbo car, you are going to have to maintain it very well.
if i were u, i would get a supra. but hey that's me.