Both churchill and comet lack proper anti-tank and anti-inf capabilities in 4v4 for their cost. To be more specific:
Churchill is slow and therefore will not be making any flanking maneuvers which forces it to engage against frontal armors of axis tanks. But its gun struggles to penetrate frontal armor of a panther or anything bigger. This causes it to become damage sponge which goes and in and out of the battle constantly while causing little damage to opponents tanks/emplacements/infantry. While doing so it only results free xp to axis/okw anti-tank units.
Comet misses shots too often against infantry which causes its damage to be unpredictable. You will often have to back away even from a single volks squad to avoid getting fausted. Panther also seems to be penetrating comets armor more consistently when engaging frontally even though their cost is similar.
What amplifies the need of UKF player having to rely so much on these units is that UKF lacks proper artillery and tank snares. You are either forced to feed xp to opponents tanks with churchill going in and out or going all-in tank rush. The faults of UKF tanks were previously complemented by incredibly strong call-in strikes like air supremacy, mortar cover or artillery cover which made all-in tank rushes viable. Now that they have been tuned both tanks feel like have been left behind.
Both tanks should be able to punish approaching infantry blobs hard. Personally I think churchill should have more anti-inf firepower than comet and comet to be on par with panther.