4-stroke pro's:

- they're quiet
- they're lighter for a given displacement
- they're sometimes ligher for a given power
- once set up, they're less problematic (ie: more tolerant of mixture etc).
- they can use more efficient props in slow planes(more thrust per HP)
- *some* (but not all) are more fuel-efficient than 2-strokes

4-stroke con's:
- they cost more to buy
- they do require regular (but not frequent) maintenance
- they do prefer a little more nitro than 2-strokes
- they're not so good in *fast* planes (inefficiencies of very coarse-pitched props)

that's just off the top of my head though.

I have four 4-stroke engines (2xSaito, 1xTT, 1x HP) and they're all wonderful engines -- each with its own personality, strengths and weaknesses.

I also have seven 2-stroke engines and *most* of them are great (the TigerShark is *useless* and I'm not so sure about the GMS -- it's worn out already and never ran that well). They are 3 x TT46Pro, 2 x ST90, 1 x GMS32 and 1 x TigerShark 56AR.

The problem is that I just *love* engines, no matter what type -- but, as they say "[a] different [number of] strokes for different folks"

However, I think that everyone should haev at least *one* 4-stroke -- just so they can experience the difference for themselves.