Having shot both, I'd steer you towards the SIG.
In my soon-to-be-flamed opinion, the XD is an oversized, oversprung, underengineered weapon. It's almost like Springfield Armory asked "How can I make a 1911 look like a Glock?" and the answer was "XD!" The slide is too wide and blocky for CCW; the poly grip doesn't fit my hands --- in fact, the thumb depression ends up slamming into my knuckle with each shot; the grip safety is redundant in this gun in light of the trigger safety, which I also find uncomfortable; finally, the magazine springs and recoil springs are stiffer than they need to be. Furthermore, what is the point of a single stack .40? If you're going modern, make it a double stack. However, it seems to shoot straight and go bang every time.
In contrast, the SIG feels better in my hand (still not a fan of the grips, however), shoots well and has a sterling reputation. I also find the aesthetics more pleasing. Also, SIGs also seem to fire every time. Expect a higher resale value for it if you wish to part ways.
Don't balk at the higher price --- you can ammortize it. That is to say that the extra cost of the gun will fade with time. If you hold on to the gun for 20 years, that extra $200 won't be much.