Yes, you do get more xp from the fishing rod. The bow may be quicker and easier, but taking the time to dig up the bait and patiently wait for a nibble gives you something like two times the xp or more than just snagging the fish with an arrow. I think it's because that while shooting a fish with an arrow is an incredible feat, you learn more about the fish and its habits by patiently watching it and understanding its diet and psychology. "mmmmm, worm yummy. Ow! jaw hurts. can't breathe, can't breathe. Monster hitting me with oar..." There is much wisdom in that.