Only a handful of large companies make actual RAM. Many other brands buy the chips and assemble the sticks. Fairly safe to stick to the big boys, with a lifetime warranty.
OEM manufacturers for Apple and other major brands:
Micron (sells direct as Crucial as well)
TSMC
Hynix
Samsung
Toshiba/Sandisk
Nanya
RAM is a commodity, so prices fluctuate by both supply and demand, and sometimes by manufacturer. I tend to recommend Crucial (Micron) because they have easy ordering and good service...but sometimes they don't have a good price on a particular product.
OWC gets their RAM assembled (as do many other consumer brands), and have great service and great quality in my experience. Not the cheapest, but cheap RAM may not be worth its price...if there are any issues. Found this list, and at least historically, this was accurate:
The differences between unbranded and OEM memory modules are fairly small, but typically come down to things like:
- PCB layout (optimized for electrical noise, proper signals termination, etc.)
- quality of solder used (in theory, should be whatever is recommended for use on the equipment bonding the DRAM to the PCB; in practice, I suppose it could vary [lead vs. lead-free, purity/formulation of solder, quality of solder joints, etc.)
- gold vs. tin leads (e.g., amount and quality of the plating on the "fingers" where the memory module plugs into the socket)
- DRAM binning (e.g., quality of DRAM used--just like slower CPUs are actually faster ones that failed high(er)-speed verification, DRAM is graded on speed and latency, with slower speed/higher latency DRAM going onto different memory modules).
- Testing (the number of tests performed and the amount of time tested, for example, memory meant for overclocking may get additional factory testing).
- Warranty length