I had a 13' otter (18" tubes) for 2 years, then upgraded to a 14' sotar with 20" tubes and way more kick. Go for the bigger boat, more gear, and will handle bigger water much better without being much bigger for fitting down tight places. I also disliked the floor height on the otter, it was way too high and my knees stuck up. I don't know about the ones you are talking about specifically, but there's something odd about the otter that way, and the smaller tubes don't help.
I am a river, babe - I've got plenty of time, I don't know where I'm going, I'm just following the lines..... - "We are water" by Shaye