Comet has 18 pop. And is less mobile than crom. If you want to drive off infantry capping your far point, crom is better, its role is like late game t-70. If you want to attack axis directly, church is better with high hit points.
Not mentioning that comet still loses to panther 1v1. Comet still needs buff imo, if mg buff applys to crom.
Moving from one side of the map to the other relies on top speed. In this a vet 0 comet is only 0.1 speed(6.9 vs 7) slower than cromwell which is marginal. With vet, the comet is actually a fair bit FASTER by 0.6 speed (9 vs 8.4). Coupled with the fact the Comet has more AI tools (WP and grenades) than the cromwell, your mobility argument simply does not hold up at all.
Obviously the comet loses to the panther 1v1, the comet has a lot more utility against infantry and is "more mobile"-which is apparently a HUGE advantage...
I'm going to pretend you were joking about the pop cap issue.