the stopping power of a 9mm glock is equal to that of a 9mm sig. its not the gun its the bullet that stops the BG. but if one of the guns has a longer barrel than the other it will give the bullet more velocity and therefore more stopping power. i'm going to compare the Glock 19 to the Sig 228 since i know the most about them but the same comparison will hold true in comparing a Glock 17 to a Sig 226 or a Glock 26 to a Sig 239/225.
most people will find that the 228 will have less felt recoil than the G19 since it weighs more but the G19 has a polymer frame which absorbs recoil so it too doesn't have much recoil. recoil isn't that big an issue with 9mms unless your comparing sub-compact guns. i find that beretta 92's recoil extreemly softly and that glocks and sigs recoil a bit more but its not much worse.
glocks tend to point on target faster for people than sigs since they have a more natural grip angle. i find that the G19 fits my hand really well and it points very well for me.
glocks and sigs are very reliable guns. if clean and properly lubricated at the range you should not ever have a problem with either. but glocks will work in more situations than sigs will. you can go without cleaning a glock for a year and it should still work properly (i wouldn't advise this) but a sig would most likely jam. also glocks will work after being dropped in sand, salt water, mud, and many more things where this may cause a sig's action to jam. glocks can be run over by cars, dropped out of windows 400 feet in the air, tossed over your head, etc and still work and they even won't fire the round in the chamber thru all this. another plus is the tenifer finish on glocks is much more rust resistant than that of sigs.
last i heard Chuck Taylor's G17 had 165,000 rounds thru it and was still going strong but that was about a year ago. i doubt that could be possible with a sig. there are many rumors going around about sig's aluminum frames cracking and glocks constantly KB'ing but as i said these are rumors. both those things do happen but a lot less than people make it out to be. both guns have a good chance of outliving you unless you shoot a lot. i have seen a sig 226 that had numerous +P rounds of 9mm thru it and it didn't work reliably because it was too worn in. but IIRC the factory said they'd fix all broken or worn parts for a pretty reasonable price.
as for accuracy i find both guns are very accurate. i shoot glocks more accurately because of the trigger and that the gun points very well for me. i don't like DA/SA guns because unless i really slow down i pull the DA shot off center. with training i could become a better shot but i have my glocks so i'm fine
. if you put both guns on a ransom rest at 25yrds the sig would most likely produce better groups but i don't feel that matters. they were both designed for Police/Military use and are more than "combat accurate".
some other things to consider: for the size glocks offer more firepower. the G19 and 228 are similar sized but the G19 holds 2 more rounds. the G17 also holds 2 more rounds than the 226 and the G26 holds 2 more rounds than the 239 or 225. 2 rounds isn't much of a difference though. also when comparing like sized glocks to sigs the glock weighs more and is smaller. i remember when i was buying my G19 i was also considering a 228. i held the 228 and even though i could never conceal carry (live in NJ) i thought to myself how could i ever carry this gun its pretty big and quite heavy. then i picked up the G19 and it looked quite a bit smaller and was definetly a lot lighter.
glocks cost a bit less. i bought my G19 for $459 but since then the price has risen to about $500. sigs can be found somewhere in the $500s or $600 depending on the model. hi-cap mags for both are quite pricy.
i would go to the range and rent both these guns to try them out and see which you like better. you may find you shoot one a lot better than the other. the glock trigger take some getting used to so you should try both guns several times. i know i seemed to favor glocks but they are both very good top of the line guns. i would feel well armed with either.
