I would shoot both - you will find a huge difference in ergonomics. Capacity not a big issuein my opinion as you can keep a spare mag (If 9 is not enough). The 1911 wins my vote
I have been thinking of getting another gun for HD(Glock 22) but I already have the Sig 229 .40 and a 1911 and feel completely secure using either. I would go with the 1911 over the glock.
I ordered the G21 with the OD frame yesterday. Hopefully it will be in soon. The biggest reason for going with a Glock was that I got the discount. Night sites and 3 mags for $525 is a deal that I couldnt pass up. Ammo wont be an issue since I reload .45 for my Dad's G30. Im starting to see an advantage to standardizing calibers and firearms.