Which wakeboard would you recommend?
 

Intermediate skills

http://www.evo.com/outlet-shop/2012-...ards/mens.aspx

boat or cable?

do you like fast boards that ride high and carry a lot of speed or do you like boards that ride a little slower and allow you to get a little more of an abrupt upwards pop?

Boat-'97 sport nautique.
Wake is so half pipe, I wish I had more transition like Malibu but I save gas with less weight and gt40

Which type are easier on the knees.
This nautique wake is beating me up by the end of the day on the landings.
Also, is a lighter board always an advantage ?

There are several great boards on that page: Viva, One, District, Watson, Harley, Franchise, Murray. Those would be my quick picks--I don't think you can go wrong with any of those. All are pretty easy to ride.