I like Sig and XD a lot. Sig is makes a solid accurate gun. I haven't tried that exact model of Sig, but for me the XD is better. It just a feel and ergonomic thing though. I'm not much of a Glock fan. Aside from feel and sites the Glocks feel more snappy on the recoil to me.
I'm not sure why you want to sell the Sig. If you like it I'd keep it and maybe add the XD if like that in addition. If you aren't happy with the Sig I wouldn't think of the XD like a Glock even though they have some strong visual similarity I like the XD much more and I like the addition of the grip safety on the XD.
I can shoot equally well with either Sig or XD.