Magnum = Great engines, put fuel line over high-end needle valve to prevent migration and leakage. Has ball bearings so it may live longer than non-ball-bearing engines.

OS = Great engines, but the LA version (the only OS .15 SSC legal) is not a ball-bearing engine. Runs good out of the box, took a little longer to break in and reach peak potential than my Magnum .15

TT = My .40 is a great engine on my Quickie 500 Viper. Lots of power, nice idle, easy to set up. Long break-in, but that may just be me since I was going to be racing it. I cannot comment on their .15's though, and some things do not carry throughout all engine sizes even with the same manufacturer.

Hope this helps,
Will