I'm a Spuffy shipper 100%, and I'm also a diehard Cangel fan. Bangel was sweet for a first love, but I think both Buffy and Angel went on to have deeper, more fulfilling and meaningful relationships with Spike and Cordy - relationships that were built on friendship and trust and not just love at first sight and shared misery. Spike and Buffy changed each other - as did Angel and Cordelia - in the best possible way. They brought out the best in one another and truly completed and complemented each other :)
I've always been a Spuffy fan and always will be. While I understand and accept that Bangel relationship were needed and were important for the story and Buffy's development, I feel like they were more of a first love kind of thing and while first love is a huge deal and indeed can have a great impact on your life, it doesn't mean it's going to be your only love. And I feel like Buffy and Spike built a stronger relationship based on mutual trust and by the end of the show they could rely on each other the way they could never rely on anyone else and they proved it countless times in season 7 that they would trust each other with eyes closed. They sticked together even though after all the tough and dark stuff they've been through it would have been easier to just walk away and give up on each other, but they never did. The connection they formed helped them to survive and save the world together.