What's most often considered the best brand of Ram?

All well-known brands are basically the same, as long as you get it from a reputable source, you're good, here is where you can buy it from iFixit.

Almost all RAM carries a lifetime guaranty. I've seen maybe 10 sticks of bad RAM in thirty years. Most RAM failures are caused from ESD (electrostatic discharge). Drag your feet on the carpet and hit the screw on a switch plate, that's ESD. Only 1/10 of that amount is necessary to damage RAM. I've seen no reason to buy the high end RAM. I've bought mine from www.ramdirect.com for about the last 15 years. Ther're good people and have helped me with some answers on this site.

Crucial Has always been the best for me, i have bought ram from them since the late 1990's

The technician from my town says PACCOM is a good brand and is compatible with MAC. All my extra rams are from this brand.

I think the best RAM is the cheapest RAM that has exactly the right specs. I don't think there is any RAM that has the correct voodoo magic and therefore somehow always works better with Macs...if RAM works with Macs, it it's because the specs are exactly right, and if it doesn't work well with a Mac, most likely some aspect of the specs were ignored, or too vague in the description of the RAM to be determined.

In my opinion the main value of a name brand, besides a warranty that is easy to take advantage of if need be, is that the major players have really nice websites that make it easy to determine that you are getting the correct RAM. Unfortunately, however, you will pay a premium for that convenience. And then again, a website like dealram.com is very easy, and allows you to buy more generic RAM as well.

RAM is one of those things, like hard drives, where there are really only a few companies in the world that actually make the product, so quality-wise I've never really noticed too much of a difference.

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