Make sure to check Silver Bullet's used case. According to their website, they currently have a full size M&P9. The only XD they have is a XD-45, but check the case as normally they have a few in the case that are not on their website. (
http://www.silverbulletfirearms.com/index.php?view=category&catid=1&option=com_joomgallery&Itemid=120)
As far as size goes, to each their own. TheQ has considerably more experience than I and is more comfortable working with a full size. When I OC, I normally carry a full size 1911 (big and heavy). However, there are times when I just want to be discreet and for that I went with a much smaller option. I have two tools for two different uses as opposed to one tool for two uses. The up side is each tool performs it's specific use better, but the down side is more cost, and I am unable to transition as easily. I do think I have a slightly smaller frame. I'm only 5'10" 185. I have no doubt Q is competent at concealing a larger firearm, but I'm not to his level yet.
As far as round count, I see this as another to each their own. When things get hairy, who doesn't want more rounds, but on the other hand more rounds equals more size and more weight. If those two things are going to make you less likely to carry, then they need to be considered. My XDs is a 5+1 (but in .45 instead of 9mm). The way I look at it, that's the same round count as a revolver and the chances of me needing more than a few rounds should things get hairy is very slim. Carry more rounds if you can, but make sure you carry first.
I hope some of this puts my views into perspective. That way they can be better applied or discarded as needed.
