I can think of several valid reasons, most of which have been mentioned already, but:
Originally Posted by C hawk Glock
1. The Walther is heavier, which means it will handle recoil better.
2. The .40 caliber M&P Shield has had a lot of problems; the Walther; not as many.
3. The PPS is more readily available than the Shield. You can get a used one for a decent price.
4. The PPS seems to be more "accurate", according to people who have fired them both.
(Plus it's conceivable someone might prefer the PPS trigger or appearance, or is working on a Walther collection, or something...:wink:)