James has arguably the toughest job to do as ANYTHING, no matter how insignificant it may seem, can affect his voice. Since everyone has a voice of their own but not everyone plays guitar/keys/drums, it's easy for people to hear when James is off but not so much when the other guys are. It's a difficult career but I think he pulls it off perfectly more often than not.
I hope with MP gone James will up his front-man stage presence. I've always felt it very lacking but that could have been cuz MP was doing so much to engage the audience from behind the kit. Now is his time to shine and engage the crowd better/more.