Now that I've had it for a bit and gotten to carry the Glock 20, I figured I can give a brief synopsis of the change.
As you can see from the following photos, the Glock 20 is considerably larger than its subcompact brethren
Surprisingly though, it carries much, much better. The difference in comfort is substantial and it's all about the shape. The 20, with holster and 15+1 rounds weighs in at 2lb 13.35 oz while the 29 with holster and 10+1 is 2lb 6.4 oz (a difference of only 6.95oz). The Kel-Tec P3AT weighs in at a whopping 12.55oz with holster and 6+1 ammo.
There is definitely a greater print chance with the 20. The rear sight can poke out if I cant forward, the butt of the grip will slightly show if I cant normally. Loose shirts (which I generally wear) conceal this fine.
The Minotaur (MTAC) from Comp-Tac is starting to break in and becomes even less noticeable than it already was. I can tote around the 20 all day and not even notice it. The 29 fits in the MTAC as well (as does the G20 in the CTAC, however the muzzle pokes out the bottom, increasing the risk of dislodging the firearm when seated), and the MTAC adds more comfort, but still the 29 carries differently.
I do love the full size grip of the 20. Alas, my discussions with the fine folks over at Crimson Trace indicate there isn't enough demand to build a laser for the 20 as the grip shape /size doesn't fit the molds they have. If enough people bug 'em, they might (*wink wink*).
So far, happy with the pistol. The new barrel and Sevigny sights are on indefinite hold as of now as my daughter's recent surgery put a bit of strain on the finances. Starline is behind on brass until 9/15, so shooting is going to be fairly limited for a while too. Still, I'm confident in the pistol to put rounds on target and feel comfortable with it on my side.