I've never used any of those but understand the fixed timing units are real finger biters when starting. BCMA has a electronic advance timing same as the Roy Sholl. I believe Brillelli also quote three different prices depending on what EI you choose. The Roy Sholl EI option is an extra $40.00. That engine also mounts on a standard glo-engine mount which I don't like but you might. Afraid you're just going to have to make your mind up. Nobody here is going to tell you which one to buy. It's just a matter of personal preferences.