Vertical splitters are better since the splitter comes down to ground level where your rounds already are. Much less lifting.

I'm not super quick with a maul, but I can pretty easily keep up with the hydraulic splitter I've used. The hydraulic splitter is nice for the ones that have really gnarly, interlocked grain.

Until you get a log so tough, it just stalls up when you draw a splitter. Happened more than once. Usually the log is stuck so far in the wedge you can't get it off either.