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Timekeeping with the 7S/4R/6R movements is a bit of a lottery because they don't adjust/regulate them at the factory, for obvious cost reasons. I have a 4R36 turtle that gains 1.5 sec/day. Whereas the one I bought Inchpincher for his birthday turned out to gain something like 15s/day.
They are very capable of good timekeeping though. A friend of mine regulated his Seiko 5 himself to +30 sec/ month. I have owned five (!) watches with 4R or 6R movements and they've all been within COSC (-4/+6 or better).
True for many of them (and it’s the main “upgrade” over the SKX007) but you can (could?) get 4R-based Seiko 5s, especially the Sports models, for little more than a ton. Eg this one of mine (Sumo has the black version). Think I paid about £150 but later on they were popping up for £120-ish. Decent bracelet and a display caseback on them too.