The usual example of eighth-note swing in jazz...
...skipping rhythm in 6/8...
...is there any difference in how these are executed rhythmically?
...is the eight-note in swing a little bit longer than in straight 6/8?
I tend to think of swing as the 12/8 version of 4/4. So two lots of 6/8 is pretty close, watching the 'second bar' of 6/8 for emphasis, or lack of.
Having said that, there's swing and hard swing, where the rhythm is closer, but not too near, to dotted quaver/semi. Someone did actually time and work out the proportions of various jazzers, and there is a difference between bands, but also numbers. Some feel the need to be swung more gently, others harder. Suppose it depends what mood the band's in.
EDIT: some homework reveals a study which states a ratio of between 2.5:1 and 1.5:1, the latter tending to be on faster pieces, all taken from recordings of famous jazz players, so a start point of 2:1 is good. I tend to use 'Humpty Dumpty' as a start point for students. Right now, I have a French guy for whom Humpty Dumpty has no particular meaning. So, looking for a similar rhythmic name/phrase in French. Any offers?
Swing is not just about the length of the two notes, but also where the emphasis is placed. In swing, the 2nd 8th note (or eighth note following the quarter if thinking in 12/8) is stronger, with more emphasis. I think "doo-BA." The "doo" is longer, but the "BA" is accented. The accent on the 2nd note is part of what creates the syncopated feel in jazz.
If you think "DOO-ba", you will get a western-country feel as in the folk song like "Goodbye Old Paint" in which this kind of accompaniment really does sound like an old pony plodding along. Accenting the first note in the uneven 8ths also sounds like boogie-woogie. It's a very different feel.