Very similar, but Disneyland is much bigger since it is on the river and not a "stadium" show. The Mark Twain riverboat and the Columbia add a lot to the show that you just can't get at WDW.
The size of the the venue at WDW makes it a little more intimate and seem much more intense. The stadium seating at WDW means it's less likely that someone will stand up or get in the way.
Neither show should be missed, if for nothing else than comparing the experiences of each.