If they're all you can reasonably get your hands on, get them. I've avoided the PDX-1 in .38 Special based on these two tests -- a limited sampling, indeed, but I think this guy does good work...
Winchester PDX1 Bonded .38 Special +P SIM-TEST w/Denim - YouTube
Winchester PDX1 Bonded .38 Special +P *** RETEST *** - YouTube
Beyond that, I can't find much in the way of credible testing on the round, and that's usually a dealbreaker for me.
There've been a great many threads here on defense rounds for an Airweight J-frame snubby; run a search and learn much.
I think the best rounds for your 642 are:
- Speer Gold Dot 135gr short barrel +P
- CorBon DPX 115gr +P
- Buffalo Bore 158gr LSWHC standard pressure
Honorable mention to:
- Hornady Critical Defense 110gr standard and +P
- Winchester, Remington or Federal's FBI round, 158gr LSMHC +P