@pirhomania,
The plain facts are Fleck valves have been an industry standard for 40+ years. Clack valves have quickly become an industry standard also by water treatment professionals across the country. Fleck parts are readily available on the web and from independent dealers. Clack valves are only sold by independent dealers now. They have removed the sale of their equipment on-line. Just keep in mind that anyone pushing a name brand probably represents that company. So the recommendation is rather biased and they may not have had much experience with other manufacturers. Ecodyne is the largest manufacturer of water treatment because they manufacture, Ecowater, Sears, GE, Kenmore, Northstar among others. You really can't go wrong with either Fleck 5600sxt, 2510sxt, 9100sxt (twin tank) or 7000 valve. The clack WS1 valve is the industry standard for residential use. These are all available from independent dealers and flecks are available on-line.
I hope this helps,
RJ