I own a Glock 19 (a little smaller than the 17) and a GP-100.
Both are great fun, but I tend to both carry and shoot the Glock more. The GP-100 is a blast, and I think a revolver is perhaps the way to go for a first handgun. But my stainless GP-100 is more trouble to clean than my Glock, and the 10 and 15 rd. mags are more conducive to target banging than the 6-shooter.
Also, take a look at ammo prices in your area. 9mm is dirt cheap (1/2 or less the cost) around here compared to .357 mag or .38 spcl. If it costs a fortune to shoot, you won't shoot it as much. (That's why I love my .22's and 9 mm's!)
I really think you will be happy with either gun. They are both good choices.