The PT51uses the same compressor wheel as the TA49. The PT51 has a slightly larger turbine wheel. The turbine wheels were known for breaking. IMO there is little to gain unless you are pushing the Ta49 Into the 10s. And even then I doubt you would see much of a gain. If you have a Garrett housing on the TA49,the pt51 will have a lot more lag.
The only turbo I've used in the evolution of my car that crapped out for no good reason was the 51 and it did it twice. Precision didn't get money from me a third time.