Mahomes is in NFL 5 years now, Allen 4. So kind of known quality.
In my mind, Mahomes' playing level is fairly steady - with normal up and down like everyone else (this year has a ugly stretch) - but still regarded as the very top level in NFL.
Allen is still evolving, but I can say he tends to be more volatile than Mahomes ( I haven't seen Mahomes playing teams like Jags and not score more than 6 points). But his highs like the last 2 Pats game are better than Mahomes ever produced. Honestly, I, like everyone else, didn't expect Allen to perform at the Foxborough game level any time soon, but he topped that last Sunday. It will be an eye opening experience for us all if he can play near that level for the next couple of games, and if he does, I'd put him right up at the Mahomes level, if not outright passing Mahomes..