First, welcome to the forum.
I don't think you can go wrong either way.
The SD has a few upgrades and costs a little more. The black finish and night sight are a nice touch. I couldn't care less about the rail, but for those who like rails, the standard one on the SD will make it easier to buy gadgets. The lighter trigger should make target shooting a bit easier.
I have the siggy and I'm very happy with it, accurate, 100% reliable and fun to shoot.
SD9VE, American perfection!