The TBI motors had IAC (Idle Air Control) issues and I hear a lot of injectors that fail (leak or not open).
The Vortec Gen 1 were good at leaking antifreeze from the intake manifold because of the different design because of the Vortec; This usually happened around 100k, so most out there have already been fixed. The injectors are prone to leaking on older units; upgrade to MPFI for a few hundred bucks. Fuel pumps... Need I say more?
Either 'era' are great trucks IMO!!! A friend of mine had a '92 ex cab 4wd with the 350 and 3.73 gears. He could get 17-19mpg on the highway.
I have a '97 ex cab 4wd with the 350 and 3.73 gears, I get 18-20mpg on the highway and I have 200k on the factory motor and 4L60E trans. I wouldn't hesitate to drive that thing to the moon if I could!
As for choice of purchase... I would take the Vortec just because of the higher output power. You will also have dual airbags, and 4-wheel ABS. Get an extended cab, and in '97 you could get the 3rd door.