I was lusting after the Sig 556 when they were first announced but after a lot of research went with the XCR. Best decision I made. It was my first black rifle and I studied everything I could find for the better part of a year while waiting for the Sig to actually become available.
Besides the information about the weapon system I also became conversant with the "peculiarities" of the various talk forums. I'm either Consultant or SigsRule on the Sig forum, ARFCOM, CO-AR15, Coloradocarry, Silencertalk, and Warriortalk - plus a few others. Today I mainly frequent xcrforum, co-ar15 (local to me), coloradocarry, and warriortalk. The signal to noise ratio is too high on many of the others. That includes sigforum even though I have a lot of Sigs and used to spend a lot of time there.