Well the first difference between generic and branded RAM is the price, as you eluded to. Personally, I would never buy generic RAM again.
There is no performance difference, but branded RAM is more reliable because the build quality is better. Also, companies that make motherboards test their systems with branded RAM. This is because, when testing you don’t want to encounter an error and spend lots of time troubleshooting it only to find out that it’s not your product that’s erroring. Also, branded RAM sells more, so there’s more chance that the companies making motherboards will have to work with the brand. Often motherboard companies will recommend particular models and brands of RAM, because they have done testing with them. Hence, once more branded RAM is more reliable.