Did both, found I much perfer the cooler MLT.
BIAB was convienent for the sake of one pot, but it was more work dealing with the hot wort/spotty volumes/etc.
My 5gal cooler was $16, dual lined 5gal paint strainer bags was $3, and I use the spiggot that came with the cooler to drain it. Now I always hit my boil volume, and clean up's about the same with just a cooler to wash out in the tub.
Much happier with the cooler. YMMV.
Primaries: Marches Mild
Bottled: K23 (last one!)
Kegged: Harvest Graf 2014, DPA Clone, Dampfbier, Hornet ESB
On Deck: All Brews Subject to Change With No Reason - loving small batch brewing AND Kegging!