Best brand of the two is OWC. But it should not mean that what OWC offers cannot be offered by A-Tech. You can have a cheap brand but yet complete the tasks. So if you are on a tight budget, and I think A-tech is less priced comapred to OWC, then choose A-Tech, else OWC is better.
One other thing to keep in mind is the returns procedure, in the unlikely case of a bad stick. Check out which offers best and choose the one which fits your budget and requirement.