Angel and Spike were definitely different in their respective relationships with Buffy. Angel was more of the "I'll be here for as long as you need me," type, holding her hand and giving her comfort and support at Joyce's funeral. Spike was more of a "I've got your back, let's go kill some bad guys." (then maybe trying to lure her down to the cellar for a little private strategy session) type. But I saw only encouragement, support, and a genuine concern for their Slayer's welfare in either approach, never any abuse. Angelus, in Season 2, certainly was abusive, though I saw more respect for a worthy adversary in Spike's attitude at that same time (by their own admissions, Angelus loved the torture and suffering of his victims, while Spike was "more about the kill") but if you view the two in their respective ensouled states, I saw no abuse, either physical or mental (let's don't get into "I Will Remember You" here), coming fron either vampire.