The 26 for me. I like the lower bore axis. Not that you can't find good holsters for the XD's but everyone makes a holster for the GLOCK. I also like the fact that I can work on the GLOCK. Simple wins for me.
You really can't go wrong with either though. Same with the Walthers and MP's, though they are still behind in the holster deptartment. Buy what you shoot the best. Not just staight accuraccy either, do some practical shooting if possible.