I like Spike far more than Angel, he is a better character(a lot of phases and development), better friend(deep friendship with Dawn, to a point where he stays with her, when noone else remembers her and she partly lost her memories), better lover in both sexual and non -sexual terms(is ready to get his soul due to a missunderstanding and fear of actually commit rape on Buffy, ready to die in order to protect Dawn for Buffy, ready to do everything to help Drusilla, when she was sick and not to forget the sexual kink). He is capable of love and deep feelings even without a soul, I do not know if Angelus is. Additionally his concept of love and passion and love being not nice sometimes is genuine and authentic.
From that point of view i would certainly prefer Spuffy over Bangel. However, there are two other points, i consider, which make the decision not that easy. First, Buffys personality and wishes and second, what i see in the dynamics between the characters. As for the first, Buffy seems to be constantly on the search of the good, calm, nice, protective guy, even if that type never seems to work for her . Angel does represent that type of guy far more than Spike does. Additionally, Buffy seems to have deeper feelings for Angel throughout many seasons, she even kisses him in season 5, when Bangel is over for long time. Therefore, from Buffys perspective it is certainly Bangel.
The second point is the dynamics between Buffy/Angel and Buffy/Spike. Angel and Buffy cannot fullfill eachothers needs, also Angel never really feels confident to be Buffys boyfriend and is easily influenced by other peoples opinions, when they say he is evil and has to leave Buffy. Moreover, Buffy can love and accept Angel, but she never is able to accept Angelus, who is a part of Angel, because her very search and wish for the "good guy".
Spike and Buffy have totally different concepts of love and relationships, which is problematic on long term. And while Spike is able to point Buffys dark sites and subconscious wishes, giving her some things she truly needs and much more love than Angel ever did, Buffy cannot really open up for any of that. Therefore ultimately, i think it is neither Bangel nor Spuffy.
The only person Buffy really opened up with (and kind of abandoned the wish for the "good guy" in the process ) , was Faith in Bad Girls. Also i think Faith is the only one who can really show Buffy, her different sites and with whom Buffy really can connect: in terms of age, being slayer, having dark sites etc. Faith in turn, can learn to restrain her wild nature, once she connects to Buffy. So i see the biggest potential and the best match for Buffy being Faith and ship Fuffy.