Do you have big oversized Yetti paws, or are your hands on the smaller side of the scale? The G19 is a bit uncomfortable for my gigantic meat hooks during extended range sessions, and the bottom of my hand extends down below the handgrip. The G17 fits perfectly though. That said I carry a G19 every day. The G17 is harder to conceal on a 34 inch waistline. It can be done, but I barely even notice my G19 IWB.
For sim training I would get the one that fits your hand best. The G22 fits my G17 holsters perfectly, so that might be something to consider as well. You probably won't have to buy a new ride for your gat. That's always nice. You'll feel right at home on a G17 after training with a G22.
I've never seen or heard anything but anecdotal evidence that shows the G19 to be more accurate. I could be wrong but I suspect that how well the pistol fits the hand is a big part of the accuracy claims. The G17 gets a little bit more velocity out of the 9mm, and with Speer Gold dot 124gr. HP I don't need the +p for the G17. The G19 however does need a +p for that particular round to get it up to optimal speed, at least that is what firearmstactical's ballistic experts say.
My advice, and the traditional ARFCOM response is to get both. I did, and in retrospect it was a great decision.