STI. I have several STI guns and a couple built on STI frames. The difference in quality between a Para and an STI is huge. Several of the major gunsmiths and aftermarket parts mfgs are carrying special parts lines for Paras because the failure rate is so high, particularly front and rear sights (fall off, won't stay on), barrel bushings, slide stops. One prominant 'smith won't do a trigger job on a Para without replacing the entire trigger group because the metal is so soft. Paras are also known to quickly peen loose because the frames are so soft (RC 16!). On the plus side, I like their magazines better than the STIs. True Todd Jarrett wins with a Para but I know for a fact his frames are hand picked at the factory. I have many friends with Paras. Some have been unable to get a decent trigger job because the holes are drilled so far off. One guy had to get a custom made sear spring, another a specially drilled sear.
BTW, my first limited gun was a Para P16 and 'till I replaced all the stuff with good parts, I had as much in the gun as if I bought an STI in the first place. The difference was I was able to spread the cost out over a period of time that way.