Simply put, there is no disadvantage to the 7000, other than the physical size of the valve, and unless you are in a dire situation to save 3" of floor space, it is a non issue. From a technology standpoint, the 5600SXT and 2510 use traditional physical microswithces to determine cycles. the 7000 series and the 5800 series use optical sensors to determine the cycles. The 7000 valve uses a completely different manufacturing technique as well, similar to the Autotrol and Clack valves. The valve is also designed for very quick and easy assembly, unlike the 5600 and other older valves that are quite labor intensive to assemble. As to the distributor tube, it is not the same size, the "default" size is 32MM, or approximately 1.26" OD, the "default" size of the 5600 and 2510 are 1.05" od. The 7000 also differs in the brine refill, it uses softened, clean water instead of raw water for the refill. So please refrain from commenting on items that you lack knowledge of.
I have worked on virtually every control valve that has been manufactured in the past 30-40 years, and I sell Clack, Fleck, Autotrol, Erie, and about a half dozen other softener controls with distribution all over the world. Since the majority of the questions here are about Fleck, and since the Fleck product line has been the best selling control valve for over 30 years, and since my knowledge of the Fleck product line, as well as the Clack and Autotrol line are considerable, I guess you could call me "insert name of control valve manufacturers name here" guy.