I collect 'em both ways. Most completed sets which contain over 50 cards are raw (T205, 206, 207, E90-1, E92, E94 master near set, T212 Obaks '09, '10, '11, 1955 Bowman, 1961 Topps, etc.) but the smaller sets are all slabbed (T200, E93, E95, E96, E97, E98 etc). The only variances are the T210s all slabbed (working on this huge set) and the 1911 and 1912 Zeenuts near sets, all slabbed.
I do buy cards raw and end up slabbing mostly for eye appeal, safety sake and because when I am gone they will be easier to sell for my heirs, although my younger daughter (27) swears she is keeping her 1/2 of the old man's stash. She also gets first pick and is wise enough to have selected the Matty autographed baseball
