These are only my opinions on what I've seen
Odonnel SS = good power, cheap but has terminal bearing issues. None here have made it past a gallon before the bearing starts dusting the sleeve with tiny scratches. I heard Steve is working on replacing the stock 14 ball bearing with a ceramic. Everyone I've talked to swaps out the bearing after breakin with a Boca 9 ball
Jammin = runs ok, not quite the power of the others.
Dynamite = count on a gallon if your really racing it competitively. none of them have lasted more than that around here if theyre keeping up with ninjas, speeds etc..
RB = Tried many of them myself and cant seem to get any low end unless I run 1.1 springs.... terrific engines, but arent suited well for our type of tracks
Alpha = Seem quite a few pop rods at different levels of use... 1gal and up
Werks = My second choice of engine for that price range, good power, improved carb and no bearing issues. Love the Werks stuff, should last you for a long time
IMO no engine is going to make it longer than 2-3 gallons if its raced competitively without some sort of maintenence... rod, bearing, etc. I know everyone will post their 25 gallon v-spec stories... but the reality is the engine will start to loose its thump with either a leaking sleeve or timing changes due to the rod loosening up. Once the tune signifigantly changes from a long time reliable base tune, the engine is communicating with you.