For a very good discussion of both engines and their pros and cons (beyond the very good info you've received here), I would strongly recommend the blue book on 2 Stroke Engines. I'm at the office and don't have it here to give you the complete reference, but its title is "2 Stroke Engines....." Its blue and is always advertised in the back of Model Airplane News.

I bought it from Amazon.com and went from being engine illiterate to knowing more than all but the engine gurus at the field! A very good reference, and it gives detailed directions about properly breaking in both kinds of engines, the process is very different and will drastically affect its life.

See ya,
Heath