Magazines are a funny thing.
With the SA XD/XDm pistols the magazines for the 9mm and .40 S&W pistols are different. The higher capacity magazines will work in the compacts but the shorter magazines won't work in the full sized guns.
I've got a 5.25 9mm XDm and it uses the 19 round magazines. Since I don't want two different 9mm magazines in the bags/drawers I'll be buying an XDm compact in 9mm rather than an XD. I don't care if it looks funny with the 19 round magazines. If I've gone through 13/14 rounds and need more now the gun looks will be the least of my worries. Then again, I need the 19 rounders to still work in the 5.25 so I can't put the sleeves on them anyway.
I'm not complaining. I'm struggling now not to go buy an XDm 3.8 but wait for the gun show in three weeks to see what the selection/prices will be. I may not be able to hold off though.
I'm wanting one pretty bad.