The 13.8 is the better boat and was the original designed kayak, I believe, and you can tell that the hull and cockpit design lost something when the boat design was shrunk down by four feet to create the smaller version. The shape of the hull is less comfortable on your legs in the smaller version. The big boat fits like a pair of nicely broken in running shoes. Just great.
Both boats are tough, stable utilitarian kayaks with a nice simple design. Both track well in the water, but are a bit on the slow side. They are very dry because of the hull shape and cruise through all sorts of water without any problem at all.
They are both really cheap as well, for what you get. I paid $550 for the ten footer and $700 for the 13.8 (Canadian dollars), which I thought was better value than some of the fancier boats.
The poly link plastic Old Town uses is stiffer than the typical polyethylene of most plastic boats, which I like, but its also heavier. The poly link does tend to scratch easily, but superficially. This probably slows you down some, but not hugely.
The amount of cargo you can put into both boats is impressive, particularly for the 13.8. I fit the largest float bag that MEC sold into the nose of the 13.8 and there was room to spare. The rear hatch will hold a ton of stuff and then there is space directly behind the seat as well. I was able to strap in a spare paddle on both sides of the seat inside the hull and it fits easily and is not in the way.
I also like the user friendly hatch cover. More rigging would be nice (both boats come with a minimal arrangement of bungie cords front and back) but is not essential. I have the multi adjusting grey foam seat in the 10 footer and a rigid black folding seat in the 13.8 and I prefer the simple black folding seat for riding and use. The foam seat becomes uncomfortable over long paddles. here