The gas system will give the AR an edge in accuracy and the M96 the edge in reliability (albeit not a whole lot in each direction).
Personally, I'd go with an AR if picking one over the other, long-term. You can get parts anywhere, from anyone... therefore you can repair easily and you don't have the same exposure you would if a major manufacturer (Colt) tanked and/or decided it didn't care to sell to non-law enforcement or non-military.
If the long term is not a factor, you have the money to spend, and you're not wanting to eventually create a competitive rifle, get the M96.