Wow, both are pretty awesome. It's a hard choice, but Torterra means a lot to me. She was my 3rd level 100 Pokémon, and my second favorite grass starter. So, it's Torterra for sure. Sceptile's eyes are what ruins its design IMO.
Random bit of trivia:
My first username was torterrapower, the Torterrapower, then IslandWalker.