DVD box set(s)?

[HungryDingo]

Does anyone know what's different, if anything, between buying each individual season of Angel and Buffy (12 box sets in total), and buying the two comprehensive box sets, one for each show (all seasons, 2 box sets in total)? I'd like to get the comprehensive sets; cheaper and less visual clutter on the DVD shelf. But not at the expense of "extra stuff," especially commentary tracks.

Thanks!

Bored now.