Its all relative to application...28's excel at moving bigger weight, .21's spool better but don't carry weight as well... On high bite or higher gearing the .28's can pull the .21's, but on most conditions the .21's more then hold their own, especially the Bonito........ The main difference is that the .21's are more stable at RPM, as in you can run them higher,harder and longer before failure.....The modified .28's are more prone to over revving if your not careful.... The .21's are safer for continuous peak RPM...

On the dirt the 28-7 is the fastest, followed by the ROMA and very closely followed by the Bonito...The 28XZ is also quite fast, more grunt then the Roma a little less RPM.....In the end tho the Bonito is simply a badass screamer of a engine that has power closer to the big engines then any other .21, so its hard to choose against it when all things considered ........it is a real thoroughbred ..and if you looking for wide open dune running they all can deliver what you are after...... Bonito would run stock gearing, Roma would run +1 and the 28-7 will run +2......... on high bite we sometimes see issues with clutch slip on the geared up 28's...so even if they offer more power, we do lose more of that power thru the clutch then we do a .21 on stock gearing...... All the engines listed will deliver the wow factor... tho acoustically the Bonito is the most musical, it absolutely sings on top end.... the 28-7 also wails really good, the Roma and 28XZ are milder sounding for some reason.... The Clocked Bonito just shrieks, guaranteed to put a smile on your face......considering its durability and overall performance I have to favor the Bonito ....its power is beyond what you would expect from a .21, massive bottom end with a crazy ass top end...