They both have their advantages and disadvantages. I've owned both, never had a problem with either.
Sig Pro's=what can I say, it's a damn good gun. It's built well and extremely accurate. The out of the box accuracy and smoothness is almost unparalleled. Plus, there's something about the sound you hear when you rack a Sig slide that you don't get with other guns.
Will pretty much eat up and spit out any ammo you feed it.
Sig Con's=price. They're not inexpensive guns. Depending on your body type, you might have a problem balancing size and capacity. Mags are expensive, $30 for new mags.
Glock Pro's=easy to use, no frills. Plenty of aftermarket support such as sights, barrels, control levers, triggers, etc... They're inexpensive. You can get used Glocks for a $400. They're easy to maintain and easy to work on. Like the Glock, it will eat up any ammo you feed it. High capacity in relation to size. C'mon, who wouldn't want 15+1 in a G19? It's a pretty small gun. Mags are $20 a piece.
Glock Con's=some people don't like the way they look but that's subjective. Some people don't like the grip angle.
I heard one idiot, and I do use that term literally, say that, "Glocks are garbage." But that was coming from an idiot who has never even owned a pistol in his lifetime.
Of course, you hear about the lack of "safeties" on a Glock. But if you're trained well, you know that your safety shouldn't be a mechanical lever, it should be your brain, which controls your trigger finger.