In my experience, both the Rockshox SID & the Fox Float are good forks - quality construction, reliable, very tune-able, and decent warranties & customer service. It seems there's an upper rider weight limit for the SID (Probably around 160 lbs). If you "race", desire light bikes, and are a finesse rider with expert or better skills, the SID is fine. For "XC" riding, the Float is the better choice. Having said that and having ridden/raced 63mm & 80mm SID's and 80mm, 100mm, 80mm-125mm Float TALAS, & 130mm RLC Floats on hardtail & full suspension bikes, I must say the Fox Float is the superior fork in most riding/racing conditions. However I've had the opportunity to briefly ride the new Reba & Pike, and both performed very well. But, given your weight & XC riding preference, you should give serious consideration to the Fox Vanilla RLC. No fork has a better feel and it might be the very best combination of weight, performance, & cost.