To be honest, Samurott ended up being the best starter for me. It's got great HM moves in Surf & Waterfall, which will you definitely need (Surf more than Waterfall) throughout the game. BW doesn't see a lot of good water types apart from Samurott, so I would really recommend going for that instead of Emboar if you want an easy game. Also, considering that Emboar doesn't learn any fighting moves via level up except Arm Thrust (you have to reteach Hammer Arm with a Heart Scale), there are better fighting alternatives, not least Mienshao and Scrafty.
Emboar is solid, but it was the only starter that I ended up boxing half way through my game when playing through Gen V. Seperior doesn't have the type advantage in most gyms, but if you mass spam Coil it becomes unstoppable.
If you want an easy ride, go with Oshawott. If you want a challenge, go with Snivy.