Well, caliber wars aside, which one fits you better? they should be similar reliability-wise, I had a Sigma as my first 9mm semiauto, but I couldn't get past the long, heavy trigger pull....
It took me a few guns to do it, but I finally found the right 9mm for me, a CZ-75B
I've owned in 9mm;
S&W Sigma 9VE (heavy, gritty trigger, traded in)
Taurus PT-99 (Reliable as all get-out, would feed any 9mm ammo without a hitch, but not as accurate as I wanted, traded in)
Tanfoglio Witness (incredibly accurate, but tempermental, lots of FTF's, traded in)
CZ-75B, great 9mm, still own it and love the thing, incredibly accurate, low, manageable recoil (not snappy), balanced, points naturally, and no topheaviness or balance shift as the mag empties
is this going to be a carry gun, range gun, bedstand gun?, the 75 series works well for all of those, but may be a little heavy to carry concealed, but that weight works in it's favor to truly tame recoil
Glocks and other "Tupperware" pistols are nice and light, but also inherently unbalanced, they're topheavy to start, and as the magazine empties, they become slightly more muzzle-heavy, a good steel framed pistol trades off light weight and ease of carry for mass and balance, they're also easier to get back on target for followup shots due to that additional weight