I am no expert but I would suggest the 16. Like Maugan said, after all this time people are still making them go better than ever before. You will not get tired of it!
No Cat is going to seem slow, I know that most of the guys on here aren't to crazy about them but you might try one of Hobie's Rotomold boats. You can't hurt them, they still offer some performance and they can float alot of people and weight.
That is just my input.