I want to do some macro work, and would like some advise on whether extension tube (s) or the Canon close-up lens adapter would be the better way to go.

The lenses I would be using them with would be either the 24-70 2.8 L or the 70-300 2.8 L USM IS. I'm aware that the 70-300 mm lens would need the close-up adapter lens.

I guess I'd like to know which route would yield better macro photos - the 24-70 with extension tubes or the 70-300 with the Canon close-up adapter. What would be the approximate distance to subject with either combination, and which would yield the best quality?

Thanks in advance!