I have both the older (non-locking) Wave and the predecessor to the Rebar, the Blast.
Shinyedges nailed it.
IME, the primary difference is whether or not you want or need access to the MT knife blade.
I always carry an EDC knife for general wood work and food prep. When I'm working in the yard or in the shop, there are a few tasks where I want a knife blade but it's going to totally foul the blade. Opening up fertilizer, insecticides and petroleum products are examples. I tend to carry my Wave for this sort of work. I use the Wave's blade for stuff I don't want on my EDC blade. I should emphasize that I think MT knife blades, as a group, just totally suck compared to a real EDC knife. I'm not going to sit down and tackle a hard wood working job with my MT knife blade. Just too frustrating.
My Blast is the tool I carry every single day in my daypack. It's always nearby. It's lighter than the Wave and packs in more tools than the Wave. I use it as my "I have a shot of fixing whatever needs to be fixed" tool.
Now... the Rebar is a bit different than the Blast I prefer the Blast to the Rebar. I like and use bit drivers but not on my multi-tool. For my Blast use, I prefer screwdriver blades that cannot be lost. For construction work, where I'm using the drivers hard on a regular basis, replaceable bits make more sense, despite the chance of them getting lost.
Wave - external knife for dirty jobs, heavier, fewer tools - best for dirty work, construction
Rebar - lighter more tools, no external knife - more versatile for general DIY utility work