...I'm taking the leap from extract brewing to All Grain and I'm torn on what equipment to buy. ...
I studied the info on all the options, and looked at some 3 & 2 vessel systems owned by friends. In the end the elegant simplicity of BIAB appealed to me, so that's the way I went.
My brewing friends (with 3 & 2 vessel systems) said my efficiency would suck, and it did until I bought a good grain mill and set it to .025. Now my conversion efficiency numbers are better than theirs.
People say the bag is a pain to clean, but that's just not true. I shake the grains off, wash it off in the sink, and hang it to dry. It couldn't get easier. Since I mash and boil in the same vessel, there's also only one vessel to clean and store.
I don't have stuck sparges, because I don't sparge. I don't have problems with pumps, controllers, etc, because I don't use, need, or want them.
I generally do 5 gal batches. I went with a 15gal kettle, and installed a drain valve (from brewhardware.com). I purposefully did not install a thermometer in the kettle, I use a thermometer/timer with a remote probe. I use a Wilser bag. My mill is the Kegco 3 roller. I wouldn't change any of those decisions.
I find BIAB so easy and efficient (from every aspect of that word) that it's almost like cheating compared to what my friends are doing.
I have no plans to downgrade to a more complicated system.