I don't really like Feraligatr, but looking at their stats, it's Feraligatr all the way. Assuming they attack each other the whole time (no stat raises), Feraligatr would work its way through Blastoise's great Defense with its own even better Attack. Blastoise, though its Defenses are great, doesn't have the best offensive stats. If it used physical attacks, it wouldn't stand a chance. If it used special attacks, its Special Attack would have a slight advantage over Feraligatr's Special Defense, but not much. Also, Feraligatr has the higher HP. So unless some luck is involved, Feraligatr would most likely win.
However, if Blastoise employed Iron Defense, Counter, or Wide Lens Focus Blast, it would be a different story. But then again, Feraligatr has Swords Dance, Screech, Scary Face, and Dragon Dance, so it could do a lot with stats.
Going by looks, I say Blastoise. =)