I'm not sure Thomas's opinions are the ones I'd hold up as paragons of clear thought and clear writing, though he certainly does have a succinct style. One of the things about legal writing is that you have to "show your work"--guide the reader from accepted premise to conclusion via accepted authority. This is necessarily a somewhat verbose process, and doing this thoroughly is somewhat in tension with doing it succinctly.

I personally think Scalia's opinions are amazing, notwithstanding his habit of writing very long inverted sentences. I'm not sure if they're the most approachable for lay people, but they are incisively clear. "Hand-wavey" is not a term that ever comes to mind reading Scalia's opinions (except when talking about drugs or gays).

Richard Posner (7th Circuit) and Alex Kozinzki (9th Circuit) are also known for their writing. I like this one from Kozinksi: http://notabug.com/kozinski/kremen_v_netsol