Givin' the nod to...
Glock. I carry a Glock 23, which is one frame size down from the Glock 17. And absolutely love it. Very light and easy to conceal. Even though the 17 is larger, it is still light. Some guys I know at the shop (yeah, I know everyone starts their stories like this, but bear with me) got bored and started playing w/ a scale one day. They found out that a fully loaded full-size Glock is slightly lighter than an UNLOADED Beretta. As mentioned above, Glocks are extremely simple to operate. Some people like not having to disengage a safety before firing, some people like the extra step. It's up to you.
As always, it comes down to you. Try carrying both, maybe use a cheap pancake holster to try both. Once you decide which one you like, then start thinking about a good holster and accessories. Good luck.