It's a mixed bag for me with Moon/Parker. On one hand, Moon has better height, better athleticism, and is younger. In that regard, he'd be more useful against the LeBron James's of the world.
On the other hand, Parker is the better offensive player, having a much better jumper and able to create some offense of his own. He, however, is a month older than Ray Allen.
I think ultimately I'd probably prefer Parker. With Daniels back in the fold, we have a greater need for a shooter off the bench. Plus, Daniels has done as good of a job on LeBron as anyone can expect over the years, so I feel confident that Daniels can handle SFs that Parker can't.
As for Shaq, I know we can compare him statistically to Perk and what not, but imagine the effect he'd have playing with our starters, whether off the bench or not. Perk shot 60% primarily on open looks, and even then he'd often botch dunks and layups because of that stupid dribble he takes before he goes up every time. Imagine if Shaq is getting those easy passes down low. Either he shoots 80% from the field (and I don't think that's an exaggeration) OR he shoots a comparable figure to Perk but makes everyone else around him better due to the defensive attention he commands.
