Maddison has great ball-control skills, average pace but OK for a midfielder, defensively I think he is OK, can help during the build-up, can shoot from the distance, takes free-kicks, so great player in overall..
Bellingham is like a generational talent and what I like more about him is his ability to play number 6 position as well if needed.. You can't play Maddison there, but Bellingham could, like Gundo does sometimes..
So, if I had to choose Bellingham, of course, but considering we have Phillips and he should be that player who replaces Rodri there if needed, Maddison will be a great addition as well for that LCM position..