I take Big Al any day for a number of reasons.
Big Al can get a shot of and be a bailout guy if needed. Not a great one, but we need all we can get.
Big Al can manufacture 20pts every night in a number of ways: low post buckets, midpost jumpers, putbacks, weakside flushes from Rondo, and, most importantly, by drawing fouls and hitting the shots. His great hands will make him a great target for Rondo, and he can run the floor for a big guy.
On defense, he's decent on-man and as a helper, but weak in getting back and s/r defense. Can protect rim with help blocks. He has great hands to eat rebounds.
Big Al could keep KG playing for two more years.
That is so much better than what Josh Smith brings. So much more.