Nothing really changes for the game, ending wise I will spoil it for you.: SPOILERS::
Bhelen: Although vicious to get the throne, killing one brother and pinning it on another, he actually make Orzammar more fare and starts to disolve the caste system.
Harrowmont: Was the likely choice to take over the throne, kind, honest and fair. Unforuntately if you choose the the conditions in Orzammar get worse as the class divide grows. --- "Carter, hand me my thinking grenades." Peter (Family Guy)
Is it possible to side with Jarvis? When you meet her, it initiate a conversation. It just seem like you can.
Is there a way to meet her before you meet either Bhelen or Harrowmont? --- Caine: They'll kick my ass out there! God: S'all good. They mess with you, they mess with me. And they wouldn't like me when I'm angry.
Bhelen is a ruthless bastard who will do whatever it takes to win. He never considers cheating (lying, stealing, intimidating, whatever) to be anything more than the most intelligent path. That said, he's also the one who wants to abolish castes and strengthen ties with the surface. Not a nice guy, but he gets things done.
Harrowmont is a kindly old gentleman who never wanted to be king and is only running because he promised his friend he would. Believes in the Caste system and feels dwarves should actually back *away* from the surface. He is honorable, just, and kind, which is just about the worst combination possible for any dwarf looking to get into politics.