Both are great handguns. I would have to say for first gun, why not get the 9mm or step up to 45? =P 9mm will be easier to shoot with less felt recoil, still packs a punch, and doesnt cost as much to shoot.
I love the beretta 92fs. Just super smooth.
XD is a great fit in the hand.
The guys here really give the good advice... the beretta is like driving an old school muscle car.... proven design and it works. The XD is like a modern import. Gets the job done, but sleek and sexy. It all depends on your flavor, esp if you want a metal gun or a plastic gun. go rent them both... or buy them both. =P