this really depends on alot of things. mainly track conditions. i race XC and i use maxxis bighorns 25" on hiper wheels with tireballs inside but i would not suggest this for MX because they are verry heavy. and will hurt you more than they help you. now ive herd alot of good things about the maxxis cerios but the 1 big downfall they have is ive herd they are horrible in mud mainly being that they dont clean out well. also you must also look at is how rocky is the track you want tires that are thick enough to handle the track but thin to keep rotational mass and weight down. tires are really a driver preference tho. would you rather have oversteer or understeer? this could also fall back to track types. i like a bit of oversteer myself. tires are a big thing of preference just look around and look at your driving style and normal track conditions. and remember tire pressure can completely change the way a tire performs.
hope this helps
I like the ITP Holeshot SxS tire for racing. I have tried both the Bighorn and Bajacross and found the Holeshot just handle alot better. The only thing with the Holeshots is you need beadlock wheels because the sidewalls are a little weak and will debead without. Tire is a 6-ply just like the Bighorns only alot lighter.
I have a few WORCS races in with some MX also, I run the Big horn 2.0 on the rear (26"). I like them and run the 9" wide on a 7" wide wheel, I like this set up because its light. Plenty of traction with a 1000lb utv.
I just started running the 26" MAXXIS 4 speeds on the front, I'm happy with them. Again, there light. I dont see any reason to run such an aggresive tire (bighorn) on the front of my RZR. The regular big horns are boat anchors.
I race XC (TORN series) and have used the 26" Maxxis Vypers (fronts were 9" wide and rears were 12" wide) last season. This season, I just switched to 27" Dirt Commanders (9" wide on all 4 corners). So far, I like the dirt commanders a little better b/c I get a little more ground clearance and they still hook up well in all kinds of terrain (haven't yet been in mud tho).
The name of the game in short course 900 is weight and tire spin. If you can save 10 lbs to the wheels that is day and night in your horsepower to ground ratio. I race Worcs and desert. For short course I'm running 28"x9" bighorn 2.0 on methods wheels on a all 4 corners. The total weight is 34lbs. For desert I'm running 28x10 Rock-a-Billy's on sti hd. The total weight of these is 44lb. no comparison as far as bottom end power with the lighter tires.