My $0.02, for what it's worth:

The Merganser will take a bit longer because you have to stitch the deck together like you stitch the hull, but it will mate to the hull with almost no forcing. The CLC deck requires you to force the deck to bend down to the shears, and to do this you will need a variety of bungees and cargo straps and a friend, but it will go faster.

If you like the idea of flush hatches, the Merganser will be the better option. It can be done on the CLC, but you need to reinforce the area around the hatch opeining and glass some reinforcements into the lid to keep it curved.

CLC also has a sale going on, so you save $75 off of a kit.

I'm your height, 5'10", but weigh 185# -- ideally I should be at your weight. If I were, I'd go with a 17' boat if I planned on primarily day trips. If you plan on doing a lot of camping out of your kayak (or plan on eating lots of super-sized value meals and getting up to my 25% body fat :-) I'd recommend an 18' boat.

If you're up to doing one from plans, you might check out the plans that were in the Fall '94 issue of Sea Kayaker -- Chris Cunningham's 18'x21.5" stitch-n-glue. Check out Ross Leidy's at: http://ross.secant.com/

Dean