Ahh... the great foil/no foil ribs debate.
I have done them both ways. The 3-2-1 method will almost always turn out fall off the bone ribs since they are braised in their juices in the foil. It is pretty much a fool proof method as long as you don't try to go only by the clock. Even with 3-2-1, you have to often adjust a little here & there based on the current conditions.
For the purists, foiling is heresy. A lot of folks -- even inexperineced ribmiesters -- can turn out delicious ribs without foil Unfoiled ribs are more likely to have a little tug to them rather than fall off the bone.
It really comes down to a matter of taste & time. I do them both ways & have good results both ways. I probably use foil about 60+% of the time however.