Should I get a 10 foot or a 12 foot kayak?

I weigh 235 and I am 6'3". I can't fit in most kayaks I will use it on some slow floats in Missouri rivers. I will also use it for fishing. What are the pros and cons for both 10 foot and 12 foot kayaks. I have looked at 10 foot Ascend kayaks from B Pro Shop and 12 foot Dagger Axis from REI (It is a bit too pricey, but I love the pit). I wish I could find a new or used Dagger for cheaper.