I think the pros and cons of each have already been very well articulated. If you can only have one of these for the foreseeable future go with the versatility of the Compact. I agree with many others that the Shield is a good CCW gun but not great. It's size prevents it from being great. I say this because its very easy to get spoiled on a micro compact pocket gun like the PM9. I say this because I don't routinely carry my XDs and it is small, but not next to something in the P290 or PM9 ballpark. The Shield is nice but over time you will want to go to the range and practice more with the Compact, it's capacity is excellent, it will eat any ammo you throw in it, and its as reliable as the day is long, and will provide great nightstand duty.

I would tell anyone this, say if we were talking about the PPS or even XDs instead of the Shield. If your primary goal is to source a gun specifically for a CCW role than get something truly pocket friendly like the CM/PM9, P290, or even a Nano and be done with it. Otherwise say hello to the M&P Compact.