I've owned a Glock (17) and Springfield XD. I like the XD better. But the Glock was great also. Unfortunately you just missed all the $599 XD's at questar.
You woulnd't go wrong with either. You will find Glock parts more common like mags and disconnectors to make your trigger lighter.
I know this is outside you're list..but the M&P 9mm is really easy to shoot.
The grips for the XD and Glock ar also different. Pick the one that feels best. The best fit will make it more comfortable to shoot, without having to have an awkward feeling grip to shoot accurately.