Brands don't matter as near as much as reading labels. Some labels with say the label dose is two tablets or capsules. Some like the expensive brands but many find the house brands like VitaCost do fine.

As I stated in the comment pasted from my PM reply, B-12 in the methyl form is best. Magnesium that is not mag oxide is an important bit of information to get from the label.

What is more important is to get started rather than put off starting until you define the best possible brands, etc. The vitamins sticky has good info and a link to a more recent updated version of the regimen.