12 years late but here's my 2 cents: it's not the brand of ram, it's the brand of the ram CHIPS. there are 3 main brands that produce ram chips: hynix (cheapest, but typically higher latency and lowest reliability); micron (server-grade with medium to high speed and high reliability); and samsung b-die (fastest, but most expensive)
but for these imacs, in 2022, you're usually capped at ddr3 at 1066mhz anyway and should easilly find new/refurbished hynix that are reliable too (all the unreliable ones won't have passed the refurb test afterall, and iirc they pumped a lot of r&d into their fabs to increase reliability), just make sure the latency timings are 7-7-7-20 or lower, run 8 passes !minimum! using the bootable version of Memtest to check for any stability issues/DoA transistora (nobody's perfect afterall, it's thermodynamically impossible any system can be >96% efficient if you believe Carnot), and you should be set for life.
after seeing how corsair f'ed people over by swapping out samsung-b dies for hynix dies in their ddr4 ram, causing tons of people to get less than advertised speeds and unstable overclocks, i never trust the aftermarket vendors's brand and check who made the OEM chiplets + advertised timings vs received product