The 80/4.5 SSXL is tiny (well, sort of, significantly smaller than the Nikkor 90/8 anyway), the 72/5.6 SAXL is a beast with a bigger image circle, about the same physical size as the 150/5.6 SSXL (same filter sizes, also a beast, until you compare them to the big brother, the 210/5.6 SSXL which doubles as a heavy weather boat anchor when not making you wish for a heavier tripod and head, but oh so sharp, all of them) all are incredibly fine lenses (but pound for pound I love the 150 and find the 72 a difficult lens to use well. The 150 almost makes me look like a competent photographer, the 80 just makes me look like a bigger photographer but not necessarily a better one, and the 72 just makes me look dumber). Hope that helps?
LJS