Honestly, I'd go with Glock. The HK's are excellent guns, but the less felt recoil and their accuracy over Glocks are minimal, especially when you consider how there are tons of relatively inexpensive aftermarket parts and accessories for Glocks that can get them to have greater accuracy such as barrels and lighter triggers.
Also, Glocks are smaller, do not have a manual safety, have higher capacity magazines, and are less expensive. Also, the Glocks have better and less expensive magazines than the HK's. You can find Glock mags for $20-25 compared to $50-60 for HK.
For instance, a .45 USP Compact holds 8 rounds. A Glock 30 holds 10 rounds and is smaller and about $200-400 cheaper.
Trust me, I was torn between HK and Glock. I went with Glock and am glad that I did so. HK's are nice, but you get more with Glock.