If you want to play like a TD, the Hellcat is definately better than the KV-1S because, yeah, the hellcat is actually a TD. the KV1S has a bigger gun that deals more damage/has higher AP, but the reload time is abysmal and accuracy is low. The hellcats armor is nonexistant so you definately need to be more careful, but it's faster, has way better camouflage, a better profile for hull down positions, costs less to repair/rearm and will get matched against lower-tiered opponents than a heavy.
Also, given the low(ish) armor of the KV1S for a heavy, you're not going to a huge damage sponge unless you happen to be top tier tank in the match. The additional maneuverbility the hellcat provides for GTFO once you've fired a shot and been revealed will save your bacon more reliably than a few milimetres of tinfoil. The typical argument of "yeah, but TDs must turn their hull to aim" is also invalidated by the fact that most Kwanzanian TDs sport turrets.
Stats for comparison:
http://wiki.worldoftanks.com/M18_Hellcat
http://wiki.worldoftanks.com/KV-1S
For tier 6 tanks I think the real stars (assuming fully upgraded) are:
Medium: VK3601(H) (German) (Standard ammo is fine. Gold shots + KwK 41 L/58 konisch or KwK 36 L/56 is goddamn insane)
Heavy: Toss-up between KV2 (USSR) and ARL44 (French)
Tank destroyer: Hellcat (USA) followed closely by SU-100 (USSR)
SPG: Toss-up between GW Panther (German) and S-51 (USSR). Panther on an open map since it does slightly more damage. S-51 on a map with a lot of cover since it fires in a higher arc
Light: AMX 13 75 (French) is the only tier 6 light tank :p
Also, given the low(ish) armor of the KV1S for a heavy, you're not going to a huge damage sponge unless you happen to be top tier tank in the match. The additional maneuverbility the hellcat provides for GTFO once you've fired a shot and been revealed will save your bacon more reliably than a few milimetres of tinfoil. The typical argument of "yeah, but TDs must turn their hull to aim" is also invalidated by the fact that most Kwanzanian TDs sport turrets.
Stats for comparison:
http://wiki.worldoftanks.com/M18_Hellcat
http://wiki.worldoftanks.com/KV-1S
For tier 6 tanks I think the real stars (assuming fully upgraded) are:
Medium: VK3601(H) (German) (Standard ammo is fine. Gold shots + KwK 41 L/58 konisch or KwK 36 L/56 is goddamn insane)
Heavy: Toss-up between KV2 (USSR) and ARL44 (French)
Tank destroyer: Hellcat (USA) followed closely by SU-100 (USSR)
SPG: Toss-up between GW Panther (German) and S-51 (USSR). Panther on an open map since it does slightly more damage. S-51 on a map with a lot of cover since it fires in a higher arc
Light: AMX 13 75 (French) is the only tier 6 light tank :p