I have shot the Sig 226, and currently own both a SP01 Shadow and Grand Power X-Caliburs. The Sig 226 felt good in the hand, decent trigger, very accurate, but I felt there was more muzzle lift during recoil as the barrel is higher up from your grip. Also one of the guys in our club was having some problems with his Sig in that his grip interfered with the slide release and prevented the slide from locking back on an empty mag. I tried it and found I could reproduce that problem as well.
Love the Shadow, and had intended to use that for IPSC. Good stock D/A trigger @ 11 lb 8oz's and great crisp S/A trigger @ 3lbs. Solid feeling gun, with the weight making the muzzle lift during recoil very manageable. I found the rubber grips felt good in the hand, but got slippery during the summer. Tried aluminum grips, but found them too thin. Finally got a some nice aggressive VZ G10 grips and put some skateboard tape on the front strap - feels much better. A lot of parts available to tune it, and if you are shooting IPSC, there are lots of people who would be happy to give you tips, and also help you out if you have an problems during a match. I put in a lighter main spring which dropped the trigger pulls down to 8lb SA and 2lb 10oz SA.
Tried an X-Calibur and found the stock DA trigger pull felt better @ 8lb 6oz. The SA @ 2lb 11oz was not as crisp as the CZ. Just a little bit of creep before it breaks. After ~10k rounds and a detail strip & clean (and a little smoothing to some moving parts) the DA is now 6lb 15oz and SA @ 2lb 2oz and both are super smooth. One feature I love about the Grand Power line is the slide will auto-forward when you firmly insert a loaded mag. This is really great if you run your gun dry during a stage as you won't have to rack your slide after you insert a fresh mag. The rotary barrel lockup is pretty unique, and really helps the felt recoil to be less than the Shadow in spite of it's lighter weight. It also allows a very light recoil spring, so manually racking back the slide is much easier than the Shadow. The grip feels good in my hand and after I put grip tape on it, I can really lock in a solid grip. Parts and mag availability are no longer an issue, but GP mags are about $10 more expensive than Shadow mags.
For the safety, I prefer the slim ones that come as additional parts with the X-Calibur as it doesn't get in the way of my grip. Didn't like the Shadow safety, for me it get's in the way when I try to manually lock the slide back. I think I can buy shaved (thinner) safetey's but they seemed pretty expensive.
For holsters, many makes and models available fore the Shadow. For the X-Calibur, there a better selection now. I use a CR Speed WSM II holster for IPSC and a Red Hills drop in holster for USPSA. You can use the same mag pouches for the Shadow and X-Calibur.
All 3 of these guns will be more mechanically accurate than my old eyes. I prefer the X-Calibur because it has an adjustable rear site that was great for adjusting for differing ammo (eg 124gr vs 147gr) or trying out 6 o'clock versus combat sight hold.
