BlastercoolWeird says
Like most Magic: The Gathering cards, the value of Wrecking Ball Arm depends on a few consistent factors: its rarity, the printing and finish (regular or foil), its physical condition, and the set it was printed in (Final Fantasy Commander)
Built for the long game, the Bear gets closer to that +3/+3 Threshold bonus the longer the game goes
While they haven't revealed what those are, it is fair to hope for something from the X-Men, The Avengers, and more
Combined with the frankly outrageous state of things back then (4 Ancestral Recall , anyone?) leading to prolonged game states and impasses, WotC decided that enough was enough and restricted Ivory Tower
Gavin notes that there are downsides to Cranial Ram - such as the restrictive casting cost and less efficient equip cost