Recovering irrationalist, I hadn't thought of things in precisely that way - just "3^^4 is really damn big, never mind 3^^7625597484987" - but now that you point it out, the argument by googolplex gradations seems to me like a much stronger version of the arguments I would have put forth.

It only requires 3^^5 = 3^(3^7625597484987) to get more googolplex factors than you can shake a stick at. But why not use a googol instead of a googolplex, so we can stick with 3^^4? If anything, the case is more persuasive with a googol because a googol is more comprehensible than a googolplex. It's all about scope neglect, remember - googolplex just fades into a featureless big number, but a googol is ten thousand trillion trillion trillion trillion trillion trillion trillion trillion.