Good question! Truth is - I'd rather be paddling and teaching than in a store selling. I use a number of Best-of-the-Best kayaks in my instructional program. Not only do you get a great lesson, you also get to Demo the best boats on the market, kick the tires, take it for a spin, see how it fits, see how it performs, and see how good you look in it!
....you simply cannot do that in a storefront or warehouse.
Choosing a kayak is like choosing an automobile. Your choices include pick-up trucks, mini-vans, sports cars, SUVs, etc. Each are designed for a different purpose. No automobile performs well in all situations...neither do kayaks. You should chose a type of boat that you'll paddle 90% of the time.
Some options include Whitewater, Recreational or Touring kayaks.