I own the Walther P99 and the XDm.
The Walther is by far my best hand gun. If I had to get rid of all my pistols but one it would be the one I kept.
It does not have the highest capacity but the P99AS model is basically a light double action trigger. It is a very light trigger and if the round does not go off you can pull the trigger again and try the round. And again, and again. Of course after the second pull ( at the range ) I would dump the round but your second strike capabilities with this pistol are infinite. It has a decocker which most poly striker fired pistols don't have. it has an ambidextrous mag release which is a little different than most but still very functional. I have no other guns with a mag release like this but every time I shoot it I have no problems remembering and dropping the mag.
The P99 is very accurate, feels like a custom fit and has very light recoil.
Also know that the Walther is about 200 more than the Smith&Wesson 99
Which for all practical purposes is the Walther, they even use the same mag. I use both Walther and SW99 mags in my Walther and they are exactly the same.
Walther even makes the frames for the SW99 while the rest of the SW99 parts are made here in the US. The SW99 is apparently SWs attempt to better sell the Walther design here in the US. The P99 has a higher price tag on it than the SW99 and Smith figured they could build basically the same gun and sell it for less here in the US. Walther agreed so long as they made the frames. SW agreed and the SW99 was born.
I don't normally like SW poly pistols. But if the SW99 is near the same gun my P99 is. I might be tempted to buy one.
XDm is also a great gun. Low felt recoil now comes in 4.5 and 3.8 inch barrels. Both have the 19+1 capacity the great looks and function of the XD/XDm family. If you were to find a HS2000 in your travels you could pick that up as well. It is the predecessor of the XD. Made by the same company that makes the XD/XDm and it just like the XD family is a fine gun, and it uses the XD magazines so you can get hi capacity mags. The XDm is also a very accurate pistol.
I recommend you kill two birds with one stone and look at the Walther SW combo pistol. SW99. It gives the SmithWesson name and the Walther design. Rather than the Walther over the M&P. You will also save a few hundred on the price.
XDm you can't go wrong with. Both great guns but the XDm does not have second strike+ capability. But still an excellent pistol.