[voyager4520]

I own both models in Gen3.

I had to adjust my grip sometimes which leads me to believe I would use a magazine with the finger extension so I could get a better grip (I’ve shot the 26 with extension and it was no problem). The problem is that if I do that, the handle would be very close to the size of the 23 so I would be better off with the larger frame right?

A +0 extension adds the extra grip but does not add capacity. The bottom of the backstrap on the G23 prints considerably more than a G27 with a +0 extension. A G27 with no extension will still print less than one with a +0 extension, but the G23 would print more.

Here's a G26(same size as G27) with a Pearce +0 extension: http://i851.photobucket.com/albums/a...g?t=1288726115

Another of the +0 extension: http://www.pearcegrip.com/Products/GLOCK/PG-26

G27 with GAP Enterprises extension in first two pictures, Pearce +2 in last picture:
http://glocktalk.com/forums/showpost...77&postcount=6
(the Pearce +2 will only add 1 round capacity to a .40 magazine)

Sub-compact with Pearce +2 in foreground, Compact in background:
http://glocktalk.com/forums/showpost...3&postcount=11

That’s were I am having trouble because I was actually more accurate with the 27. Although they were relatively similar, my groups were consistently higher and to the left with the 23 while the 27 was more center mass.

Same here, most Glock owners report that they're more accurate with the sub-compact. I think it has something to do with the hump on the backstrap of the compact model. I've only ever shot Gen3, you might try a Gen4 G23 and see if it groups any better for you.

The 23 was definitely more comfortable to shoot, but the 27 was not uncomfortable at all.

I've gotten used to the two-finger grip with no extensions and I like it.

Capacity – 9 rounds with the 27 and 13 rounds with the 23. Assuming I carry at least one extra magazine is the 4 rounds enough to sway the decision to the 23?

You could carry the G27 with 9 rounds and carry G23 magazines as backup magazines. That's what I do. Some people have reported feeding problems if they use the extended magazine as part of the grip, I just keep my pinky off the extended magazine and I've never had any problems. You could use G22 magazines as well for 15 rounds. I have a couple of .40 22-round magazines made by Glock and they function flawlessly in both of my guns, but they're not too practical to carry.

I'm 5'11" 170lbs and I haven't carried my G23 since the day I bought my G27. I don't use any extensions, just the two-finger grip. And I carry G23 magazines as backup magazines. I have small to medium sized hands. I'd like to try a Gen4 G23 some time in the future to see if the reduced hump on the backstrap affects my accuracy. Though the early production Gen4's have a heavier trigger pull by half a pound. The newest Gen4's have a new connector that brings the trigger pull down to the same weight as Gen3. The connector will have a "dot" marking in place of the "minus" marking you see in this picture: http://tinypic.com/r/2mhdgzc/7

Also the newest Gen4's will have an ejector that looks like this(scroll down a couple pictures): http://www.glocktalk.com/forums/show...6&postcount=81