Another vote for OWC. I've been using them for at least 10 years, maybe longer, with no problems at all.
Several years back, I started using Crucial, and immediately started having problems. I know Macs can get picky with the type or RAM used, and my two imacs just did not like the RAM that Crucial was sending. The Crucial Customer support was excellent, and they had no problem sending me replacement chips twice, in an attempt to solve the problem. By the third set, it still didn't work correctly, so I bought the RAM from OWC, and gave the Crucial chips to a friend to put in his PC... where they worked perfectly fine. I have nothing bad to say about Crucial, they were great, but I stayed with OWC ever since then.