In my opinion, the only rival is the Max for Live "Modular Sequencer" by Sound Manufacture (Tim Charlemagne).
M4L, so not a VM module, you must use Ableton live and VM as VST, but it's worth it.
It is a very innovative design and you can do some grooves somehow.
But still, Vari Step Sequencer is awesome.
I just wish it could do some basic groove, but it's already so big !
