Ravenwing

[Simian]

Biker Libby is the way to go.

problem i find with ravenwing is despite the extra toughness they're still just 3-6 man squads of 3+ save marines, so for every wound you have a 1/3 chance of dying and any death takes away a significant percentage of your squad. this is especially true for the command squad. (max 5 models) they're small squads without the resiliency of the terminator.

here's some numbers for you,
20 shots at your bikers BS4 Str 4 AP5 will, on average kill, 1.5 bikers
20 shots at terminators BS4 Str 4 AP5 will, on average kill, 1 terminator.

if you assume the worst you will lose a unit of ravenwing in 3-4 turns. your terminator squad will last till turn 5. yes you pay more for the terminators but they have other advantages. No terrain checks, stronger weapons in CC, more shots at longer range etc. the speed is they biggest benefit and getting used to it is very difficult and something im crap at.

this is one of the reason im more in favour of a dualwing or triwing list. Dark angels work best when all three sections are used.