If you can afford the MT07 then there's no point getting the MT03. You save 15kg, but that's it. As someone who's owned an R3 and now owns at MT07, I can say that the MT07 is one of the best bikes I've ever owned. It has such a good motor and to give that up just to save a few kg's wouldn't be worth it.
I'm not sure how much you love your R6, but the MT07 would give it a run for it's money it terms of fun factor.
However, if budget was an issue, the MT03 would be a great little bike.