If I understand correctly, the options mentioned by the OP don't cover incident metering, right? If the meters on your d*g*t*l cameras are reading the same as the separate ones, then that's a perfectly good substitute for reflected metering, and I assume the 5D can do spot metering as well. I get a lot of use out of incident metering, but not everyone does (though there are those who would argue that everyone *should*).
Also, the 5D is a pretty bulky load compared to even a large light meter, has more things that could go wrong, and is a major expense to replace if you drop it in the lake while metering that tricky shot off the edge of the boat, or whatever. (I'm not sure what the other d*g*t*l camera mentioned is, so maybe it addresses some of these issues.)
If I were you, I'd take one of the meters out and use it for a day, then decide if you feel like it offers advantages over what you've been doing.