I haven't taken an agent out on the river, so I'm not sure how the two boats are in comparison. I do agree with caspermike, I learned to surf in the Kingpin and I think it was such a great boat to start off in. I did notice though that catching waves is harder in the Kingpin, at least for me. We were in Cataract and catching them on the fly was harder. I hopped in an all star (which was too big for me) and pretty much caught anything.
Im by no means an expert, I just think it depends on what feels best for you.