Buttons on the EC felt mushy to me, probably due to the long travel distance, I preferred the 2013's buttons much more. 2013's buttons felt much more responsive imo.
I don't really care for the scroll wheels on either one, if I had to pick between the two I'd pick the Zowie's. The DA's scroll wheel felt alright out of the box, pretty soft feeling compared to the EC1, didn't stay consistent for long. Ended up feeling about the same as some of my older intellimice, not totally impressed with the scroll wheel.
EC has much more pronounced feedback, the feel doesn't really change over time. I've had issues with both the EC1 and EC2's scroll wheels, on both mice they would skip if you were to scroll moderately fast, and on the EC2 the scroll wheel would partially lift out of the shell causing the scroll wheel to not work at all.
The build quality on both mice didn't really impress me, they both had some issues that I haven't encountered on mice that I've owned before or since.
The DA's top shell was quite creaky, its like it wasn't screwed down very much because I could feel the shell move when I would use the mouse. Scroll wheel wore out quite quickly, feels very mushy now compared to how it was when it was new, I don't think I've really liked mechanical encoders all that much though so ymmv.
EC1 had the aforementioned scroll wheel issues, the finish had a lot of imperfections (glossy white) that were quite disappointing to see, and finally the bottom of the mouse would rub against my mousepads causing the bottom to become discolored and scratched.
I'm probably being overly critical about both mice but I just wasn't impressed with the quality.
I'm not using either mouse right now, I don't really care for the feel of the DA anymore as it doesn't feel comfortable for me, the EC1 feels more comfortable (especially coming from the G400) but I can't stand the switches so I'd probably swap those out. I'd personally go with the EC1 just because it feels more comfortable and it feels similar to the G400 that I've been using, it's kind of like a fat DA/3.0.
Edit: Missed your question on the FK, the scroll wheel is similar to the one on the EC1 but the example I have doesn't have any issues whatsoever, it actually feels quite good to me. The buttons feel more responsive than the ones on the EC since they don't have much travel distance, my FK doesn't have very stiff switches either, they feel only slightly stiffer than the switches in say my G400. YMMV when it comes to the FK's buttons and scroll wheel though, I've seen people reporting varying amounts of stiffness in the switches and complaints about the scroll wheel having some of the problems that I experienced with the EC1/2.
Edited by Vikhr - 9/29/13 at 10:06pm