well how about this, there are no rules differences between ultramarines/white scars/salamanders/imperial fists/raven guard/blood ravens
the main 5 are blood angels--dark angels--space wolves--black templar--everyone else(codex chapters)
of those codex chapters some have special characters that can change the way they play, ultramarines, white scars, salamanders, ultramarines, raven guard, ultramarines, and ultramarines.
even though they use the same rules for the majority, and the special character changes them slightly, each of the codex chapters have different backstories and preference of units and weapons. this doesn't mean every white scar army is the exact same, but it is rare to find many dreadnoughts and thunderfire guns when going with the idea of white scars.
so really the question is what do you want:
blood angels--lots of jet packs, death company with furious rending no pain
black templars--kill them they just charge faster, 20 man squads with scouts/marines
dark angels--fearless troop terminators with 1st turn teleport&bikers with homers and scout
salamanders--incredible flamers, hammers, meltas, close range high tech
space wolves--stubborn, counterattack, loose unit sizes, few jump packs, leman russes
ultramarines--10 in every unit, balanced
white scars--cheap, plentiful troop bikes
raven guard--scouts, speeders, bikes, assault squads, and drop pod dreads
legion of the damned--just an elite choice now with invuln save and slow n purposeful
iron hands--techno, lots of tanks, dreads, techmarines
red scorpions--forgeworld so they get cool stuff for less points, so many apothecaries