These are my main choices as of right now and are listed in order of preference:
FNH FNS
Walther PPQ
Ruger SR40
Springfield XDm 4.5
Smith & Wesson M&P: The reason I have put them at the bottom of the list is I have read some really bad things about the customer service and warranty work with an agency near where I live that ordered them over Glock and ended up with over 70% of the M&Ps having major malfunctions and not being able to get S&W to fix them. I still like feel of the gun though so I havent written it off.
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I have fired all of these except the Ruger SR40. Of that list, the PPQ will have the best trigger out of the box. The PPQ is widely touted, not only by me, but by most gun aficionados as having the best out of the box trigger for any polymer framed hand gun. I'd rank the FNS as second best. My bro has an M&P, but I can't speak much for it since it's highly modified. In terms of ergonomics, the M&P and PPQ feel best (to me). If you're going with a PPQ, read up on the PPQ m1 and PPQ m2. The m2 has some slight difference, namely button style mag release as opposed to lever style (like HKs). The m2 also comes in a 5 inch barrel if I recall correctly.
I like the XD because of the grip safety which most people seem to hate, but knowing that it was an HS2000 and highly marked up after Springfield started marketting them, I can't justify that cost. The HS2000 was great and still is, but it's not enough to justify a name change and price increase of a few hundred dollars. I suppose the XDm is different since it's somewhat upgraded by the factory. So if you find a good deal and like it, go for it.
Try and handle an HK P30 or P30L as well. New ones are out of your price range, but used ones aren't so bad. They feel the most ergonomic of the entire lot of polys except the PPQ which feels virtually identical. The diff is that the P30 is hammer fired and the PPQ is striker fired. Personally, I like how a hammer fired gun feels more than a striker fired. Some folks don't notice a difference.
Dead set on poly guns? Otherwise, go handle a CZ 75 or CZ SP-01.
EDIT: And I disagree about getting something to conceal. Given a good holster, you can conceal a full size gun even if it's steel. Plenty people do this. Let's not forget that the shooting experience of a subcompact versus a compact versus a full size handgun is different. Can they be mastered? Sure, but you better train with it just as much as your full size one then.
EDIT 2: Be aware that the PPQ m1 magazines are not interchangeable with PPQ m2 magazines.
EDIT 3: Also try the CZ P-07 and P-09. Both are polymer CZs.