T-10 has more armour than the 277 tier for tier, more DPM, and more pen. To me the 277 is pretty skippable since it's the same tank one tier higher, not much improved, and you have to face tier 10 cancer.
Actually scratch that - most tier 10s are skippable since under WG's current design philosophy tier 10s have to play the same as their tier 9 counterparts. Is it worth it playing tier 10s? I don't think so.
That said, both of the fast heavy lines (all three if you count 430) are very good and you can't go wrong with them. @Caomhanach SU-101 is pretty shit - 263 is pretty good as a yolo