I've been playing fiddle for 3 years now, and recently concentrating on bluegrass. For me, the main differences between old timey and bluegrass is: style- oldtimey tends to be unison playing, with the melody played by fiddle or occasionally another instrument, with guitar and others doing the rythmn. No "breaks" as in bluegrass- the improvisational solos that bluegrassers are known for. Some oldtime folks are really serious about having only traditional playing in that style. For fiddles, bowing is very rythmic. Old time jams are known for repeating a song many many times before playing another. Joke is - What is the difference between an UZI and an old time jam? Ans: The UZI quits after 30 rounds. As for which is harder- that's your own call. You can be a really good old timey player, or a poor bluegrasser. Bluegrass places the emphesis on individual performance, harmony singing, and "hot" instrumentals. It all grew out of the old-timey and mountain traditional playing. Anyone with bluegrass interest post anytime.