I've owned the Glock 20, two EAA Witness models in 10mm (Match and Fullsize with wonder finish), and the Sig P220 in 10mm.
- Glock 20. Light weight, bluky grip. By far the hardest to control/most recoil and hard on my brass. I'd compare the recoil to a K-frame revolver firing stout .357 mag loads. Glock 40 might be better, but Glock honestly needs to offer the pistol with a single stack mag to reduce the fat grip.
Lots of accessories. Not bad, not great, but an average pistol in all regards. Magnaporting help this pistol some. Slow shot recovery time with powerful ammo. Physics rules, lightweight guns are comfortable to carry, but not the fastest to shoot or easiest to control, especially in a hard recoiling caliber like 10mm.
- Witness Pistol. Iffy quality control, at least the magazine issues have been fixed with the new K10 mags. Had loads of quality problems with the Witness Match, the Fullsize was better. This pistol is really great in .38 super.
Shooting dynamics were better than Glock, but disappointed in the customer service and limited factory support. Seemed like the cartridge was a little much for the design, throws brass everywhere. Heavy. A better shooter than the Glock, but I trust it less. Didn't like the fixed, milled front sight on the fullsize, since I really wanted night sights.
- Sig P220 / 10mm Single Action Only. Heavy. Low capacity. Excellent, excellent shooting dynamics. Comfortable to shoot and extremely accurate. Good aftermarket support, nice and thin with aluminum grips. Far more accurate in rapid fire due to the increase weight. Trigger is good, but not as good as a 1911. Factory night sights are a great touch.
In the end, I'd trade the lower capacity of the Sig for it's increased shooting capacity and increased accuracy. I probably shoot this pistol twice as fast as the Glock and more accurately. Capacity is great, but shot recover time matters a lot. I really didn't want to spend the money on the Sig P220, but don't regret selling the Witness and Glock 20 to buy it.