It is nice to revisit some older threads like these, that remain as reference material for many watch buyers today. I would like to add a point that seems to have been overlooked. When comparing the movements, I think it helps to realize the purpose the designers had in mind. With the Seiko 7S, the first attribute was economy and ease of assembly, followed by durability/reliability and little need for service. It has been reported that these movements have run reliably for up to 20 years without service. It was made in 1996 to refine its 7009 predecessor, and simplify it for automated production. The movement itself remains quite simple with a small number of parts and design that is reliable, but now considered rather obsolete in advanced, modern movement design. Some gears in the 7S and the date wheels are made from plastic, as with many of Seiko's quartz movements. These are said to be less susceptible to seizing up as the lubricants degrade, keeping the movements running more smoothly as they age. Tissot and Certina also have plastic parts in their Powermatic 80 movements in the escape wheel and lever. Both movements are considered to be non-servicable and replaced at the end of their service lives. In contrast, regular ETA movements are designed to be serviceable. Performance and accuracy was a lower priority in the Seiko 7S design when compared with the ETA 2824. The Seiko movements are unadjusted, and while acceptable, accuracy varies significantly from piece to piece. The amplitude and beat rate is lower than the ETA, which tend to lead to less accuracy. However, it does lead to less wear and need for service. In addition, the rate varies significantly through out the day, depending on amount of wind, and position of watch. The watch is much more susceptible to this than the ETA 2824, which was built also built with economical assembly in mind, but without a sacrifice in performance/reliability. Originally, the ETA 2824 was designed in 1971 (about the time of the Seiko 7S) as a movement for lower end watches. It's design dates to the 1950s. Due to it's economical production features, the 2824 was able to withstand the quartz crisis of the 1980s. Since it was one of few surviving mass market Swiss Mechnicals, it was improved with the 2824-2 in 1981 and offered on a wide range of watches, up to some very expensive models. The standard ETA base finishing is superior to Seiko's minimal industrial finishing, and ETA offers optional elabore finishing to high Swiss standards at extra cost. Seiko only offers comparable high end finishing on their most expensive models, such as the Grand Seiko. The 7S has since been modified as the 4R and 6R series with addition of a rotor bridge that allows for hand winding, hacking, visual enhancements of beveled plates and more finished rotors to upgrade its look for more expensive models that often have an exhibition crystal. It offers slightly better "Geneva Stripes" finishing on movements and rotors like the 6L, which kind of mimic the finishing of the Grand Seiko Movements.
As far as the Orient movements, the current F6922 movement is a refinement upon their legacy 46943 movement, which like the Seiko 7S is also regarded as a low-cost, durable, reliable movement with acceptable accuracy. But, it's design seems to be based on older Seiko movements from the sixties, like the 4006. Not that that's a bad thing, since that's a bit more like the ETA 2824. I prefer the look of Orient's sand-blasted finish to Seiko's brushed finishes. Orient watches seemed to be a better value, offering the same quality as entry-level Seiko's at a much lower price.
The ETA 2824 is definately the more advanced design.
Here is a nice
website with teardowns on many popular movements.
Seiko 7S26A movement with plastic gears and Date wheel.