I reckon two seperate vids sounds like a good idea, I don't want to stereotype machinima but by the look of their channel, the more videos you create for them the better. And especially if you can display variety to them, so that's actually a pretty good idea.
With machinima I think their main concern is quality, I've sent them numerous emails in the last year or so, all have been ignored apart from the most recent one in which contained a cod montage which i've created recently, and one of my stunt montages. They seemed to like it, otherwise they wouldn't have put the effort in to reply, stating that once we have the required things they are looking for they will check our channel once more, therefore i'm positive about the outcome. Can only wait and see what they say once this montage is done and a few others i'm working on, cheers for the advice.