Hmm. I think for me it depends on the character, or maybe it depends on the reason I like the character. I like to see Snape from the outside (in fact I have little choice since I can't get very far into his head), but with other characters I often like to see from their POV.

Or maybe it depends on the pairing. If it's more of a sexually motivated relationship I probably want to see from the less-hot one's perspective; if I'm interested in them emotionally I want to look inside both of their heads to see how they go together.