I got an Ares piston system before they sold it to Bushmaster. I really don't have any reliability problems with it, but I rather have a DI system because some accessories won't work with it, and you have to file triangle handguards to make them fit. A lot less trouble to make the DI work the way you want to.
"Democracy is two wolves and one sheep voting on what to have for dinner.
Liberty is the well-armed lamb contesting the vote." - Benjamin Franklin