I have a 14'x22" and a 16.5'x21" baidarka. The short one is based on Wolfgang Brinck's design (http://www.wolfgangbrinck.com/boats/tales/shortbaidarka.html). The longer is a LM 2-14886 surveyed by Zimmerly. I paddle both regularly and they each have their pluses and minuses.

The 14' boat accelerates better and holds cruising speed (4 knots or so) with less effort, though it doesn't glide quite as well. If you try to go much faster than this it squats down and doesn't do much more than make a big wake.

The longer boat seems to take a little bit more force to push through the water, but cruises at a slightly faster speed (4.5 knots or so) and can sprint faster than that, it also seems to have a longer glide and a bit more stability.

For most day trips I just take the shorter boat, its easier to paddle, lighter in the water and turns better. I can keep up with other kayaks, pass all the canoes, and don't have much need to go faster. The big boat gets reserved for multi day trips. The fact that there is also a 7 pound weight difference between them is also a factor in my decision, I built the big one like a tank.

I should also note that the boat you linked to has fairly sharp ends, the baidarkas I built are quite full for the whole length, so they don't draw much depth because of the extra floatation at the ends they also are a little more stable as a result.