Figured i would just clarify that you can pretty much just switch back and forth whenever you want, and that the perks you obtain will be saved even if you remove your transformation. Serana will make you a vampire lord and Aela will restore your lycanthropy.

From what I have read you only get ONE more chance to become a werewolf after curing it via Vampire Lord. So you still need to make a choice but you can play both sides a bit before committing.