There usually aren't too many fuel stations close to where we ride so hauling is mostly required.
One guy has a 100 gallon slip tank that we have used. It is nice, but I'm always leary about what else is in the tank that might cause engine problems. Another guy has a big tank under his trailer. Same issue, never know how much water has condensed in the tank over the year and who is going to get more than his share of junk.
I usually just use 5-6 gallon jugs because they are handy and fit in the trailer between sleds real easy. Plus I can carry the darn things. Also, we have hauled them on the sleds to a remote cabin or to fuel up a dead sled. Harder to do with a 60 gallon tank.
If you go with a larger tank, make sure you can get the fuel out. If you run an electric pump, make sure it works well. Lousy if you are waiting to ride and you can't get the go-juice out.