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max doesn't work with bodyparts like poser, so for any little morph you have to have the entire mesh loaded. Putting all of those morphs into Max at once is a pretty good way to choke it up, so you'll have to be judicious about what you put in. But, you can still have a 'fully loaded' startup master saved.

There's workarounds to this.  Such as putting all your necessary morphs into a "dummy" .max file, and merging the ones you need into the actual scene (morpher modifier) as needed.  Kinda like using Injection Deltas in Poser.

Quote - If your biped is expertly rigged, with good joint parameters and falloff zones, you may not need poser's JCM's or figure out how to mimic magnets. I'm not even sure if Max supports the concept of JCM's. I don't have any rigging advice, since I never seriosly ventured in that direction with max.

JCM's are basically the same thing as "Skin Morph" modifier in Max, so yes, Max supports that concept.  You can research Skin Morph in the Max manual if you want further info regarding it's functionality.  In fact, you can take that concept a few steps further using the Reaction Manager in 3dsmax, and have morphs control other actions in the scene, or each other.

Quote - I'm very curious though, what it is that Max will offer that Cararra won't, for what you're needing, is it the cloth sims?

For character animation, there's a lot that Max can do that Carrara won't.  Aside from pure rendering optimizations (which one may or may not utilize), there's things like morph-driven textures (allowing you to do such things as change to a custom bump map automatically when certain morphs are dialed in), adding to the realism of expressions, etc.  I could go on if you like.