Depends what you want it to be capable of and how much you want to spend.
If it's a pure smoker, you liked the WSM, and you just want something bigger, I'd recommend an
Ugly Drum Smoker or UDS. Operation will be roughly the same as the WSM, but capacity higher, and potentially less expensive if you can source an acceptable 55 gal drum for cheap.
If you want something that doubles as a grill, or if you want to go hardcore into a stickburning offset, or if you decide a pellet pooper is the way, or if you don't like the vertical nature of the WSM, there are TONS of options out there. When I did it, I went Kamado Joe, as it was going to become my primary grill, not just a smoker. On the Big Joe (24" round grate) I can fit three racks of baby backs without a rib rack, which is enough to feed my family. I can also fit 4x pork butts, or a large brisket, w/o issue.
So you may need to more tightly define your needs/wants a little more if you want more recommendations.