You need to consider your cam specs while looking at the standard offerings from each. I think IMM is the only one that will handle lift much over .500.

Hughes and Indy standard packages are similar, with upgrades available.

IMM pretty much only offers one flavor, but it's a good one.

I don't believe Mancini is even in the game. They weren't last year when I ordered mine.

I went with IMM for mine. It was overkill with my relatively mild build, but I've got room to grow.

I should also add that IMM gives the no-cost option to tune the chamber size from 63-67 cc.