going to have to disagree with you here. Sena improves himself and becomes someone who's worth something. He doesn't stay a wimp and doesn't whine about shit.
Tsuna on the other hand is always crying I DON'T WANT TO DO THIS THIS IS SCARY BAW BAW BAW SOMEONE ELSE SAVE ME I CAN'T DO IT SO I SHOULDN'T EVEN TRY
in conclusion, Sena is far superior to Tsuna