Spartans Vs Elites: Choosing to play spartans only?

I have been away from Halo for a while, so forgive me if I missed some info on this. Halo: Reach will bring some big differences between 
Elites and Spartans. Do you still get to choose one model as "Your" character for multiplayer? Some game modes seem to always be
Spartans vs Elites, so is it a random draw for which team, or do you have a choice?
 
Gaining some proficiency with all the new moves, loadouts for both factions kinda seems like a lot to take on at first. I suppose it
adds more longevity to the multiplayer. Not only that, I would assume that the XP gains would allow equal customization for Spartans
or Elites?
 
Any thoughts?
 
 
Edit: Nice. First forum post ended up in the totally wrong section.

whether or not they make you choose who you want to be for spartans v elites, randomize it before the game, or make your choice at the beginning permanent, they would have to make sure that there is equal customization for spartans and elites, as well as them being balanced