I haven't been playing for long, but for defensive ops and for breaking through initial defences (strong enemy tanks or guns) the King Tiger would be my choice... It's damn expensive, but it can withstand almost everything upfront... It has a slow traverse turret (i believe he needs 19 secs for the whole turn) so it's sensitive to flank attacks (sensitive for stronger guns - 76mm and above)...
I build up a quick small battle with Jumbos (76) and Jacksons and I put up various German tanks... Jacksons are vurneable but they pack a strong gun... Tiger I blew up immediately, and the others followed him soon enough, but the Tiger II stood still and kill them all...
