I'd say G21, out of those 2. Had one and really liked it. Also had a Sig, couldn't stand the DA/SA and loooong reset, even though I loved the grip and the quality construction.
The 220 is a great gun, don't get me wrong, but if I'm going to have an 8-rd .45, its gonna be a 1911. (Which I do have, and after trying Sigs, Glocks, and HKs, is all I have left)
My personal thinking is that the safety system should not impede operation of the firing system. On a Sig, the "safety" system is a long heavy DA pull. Long heavy DA pulls are harder to shoot accurately, especially if you're trying to do it quickly. So the safety on a Sig necessarily is a compromise against 1st shot speed and accuracy.
With a G21, thats not an issue. The first shot is the same as any other shot, not heavy, not long. The Glock passive safeties do not make proper trigger control any more difficult, unlike the Sig's passive safety.
Then there's the reset issue. I'm not sure if you've ever fired a Sig, but the trigger reset is looooong from shot to shot. That means you need to move your trigger finger alot more more, which tends to be a hindrance for accurate quick follow-ups.
Sure, some people can shoot the Sig quite well AT SPEED (sitting at the range and leisurely popping off rounds doesn't count, IMO), but not many. And those that do have usually tweaked the DA considerably with lighter mainsprings, etc, etc, and have work done to shorten the reset. Sig won't sell their Short reset system found in the Elite line to anyone except LE armorers, so you have to send it to them, shipping parts and labor end up being over $150. Or you can ship it to GGI and pay even more. I suspect these are some of the reasons that Sigs tend not to be favored with the competition crowd.
Which brings the discussion to cost. The G21 is cheaper out of the box, with higher capacity and better trigger system. If you want a better trigger system out of a Sig, then you'll either need to buy a 220 Elite, or send your gun off for work costing even more.
The G21 grip isn't that bad. My fiancé who's all of 5'4", 110 with correspondingly small hands handles it just fine. So unless your hands are even more girly small than hers, I wouldn't worry too much.:supergrin:
(disclaimer: these are my opinion that I've arrived at after extensive experience shooting all the pistols mentioned herein. They're worth exactly what you paid for them, and of course, your mileage may vary)