Tone wise they’re very similar. To me, the 550 sounds like the MB on steroids, it sounds huge. I played through a 550 at multi band event years ago and always wanted one, but they rarely came up second hand, and when they did it was always the wrong time for me. My current set up is Spector Euro 4LX>Fusion 550>Barefaced Big Twin 2, and I can’t see me ever wanting to change it.