Haven’t decided on whether a medium size boat or a larger boat is the direction I will go in, but welcome the pros and cons on the following bigger boats that I have demoed on sheltered water. VCP Argonaut (fit a tad big), NDK Explorer HV (fit, comfortable), P&H Quest (fit a tad big) Impex Assateague(fit big). On non sheltered water what should I expect (stability, speed, manuvering etc.) since fit can be customized later.
Here is my 2 cents
Love my explorer in standard volume; very balanced in wind, behaves in surf, not so fast. rollability and secondary stability of this boat in either hv or standard are truly remarkable. My favorite rough water boat so far.
I've owned a Quest. The Quest needs the skeg in crosswinds, weathercocks more than the explorer, much better speed. Also rolls very well. Not as maneuverable as the explorer in my opinion, (trade off for speed.) If it's really about sheltered waters then it's a strong contender. If it's about camping or speed it's a very strong contender. If it's about balance in wind without use of the skeg well.....
I like impex boats in general, never paddled the assateague. Never paddled an argonaut.
Best I can do for you.
Try smaller equivalents
If the Argonaut is "a tad big" then try the Aquanaut, and if the Assateague "fit big" then try a Currituck. Also if these two are big, you might try a standard Explorer.
My size being 6',175-180lbs, my Aquanaut is padded with about an inch on each side at the hips and half inch or so for the thighs. For heavy seas I also carry additional balast. The Sea Kayaker tests showed the boat performed best with 250lbs load.
The Aquanaut is faster than an Explorer, handles following and quartering seas better, and has a very responsive hull.
That being said, more advanced paddlers I know have an Explorer as their expedition boat than any other model.
Each of the boats you've mentioned handles quite differently and all are well designed. All will handle real seas well, though each will feel different in those seas. Try each and go with the best (snuggest comfortable) fit and the hull performance that best suits your ideal/goal as a paddler.
It's often good to buy a boat that is somewhat 'advanced' for your skill level. This way you won't outgrow it too quickly.
Unless you need extra room for gear…
…it’s generally best to buy a boat that fits you as closely as possible, but is still comfortable. Excess size means more weight to lug around and more surface for the wind to blow around. I have yet to find a single advantage to paddling an unncessarily large boat.
I’m not an “advanced” paddler
No doubt the explorer is a good boat in seas. Many paddlers use it because it is so, and because it’s been around for a long while.
As the aquanaut /Argonaut achieves longevity I think well see a lot of paddlers using it too.
by Kajak Sport was my pick. I am 6-feet and 210-lbs and the Millenium is a big boat. Out on the ocean in a breeze it is a handful and I find myself reaching for the skeg a lot. I would suggest you try to paddle the boats you are interested on a windy day in your location to see if you are comfortable with turns and staying on course.