Metafolin, that's folinic acid, right? The way folate works, there's a cycle. 5-mthf is used to link into the methyl cycle (for things like turning off histamine and estrogen and viral DNA) and then its recycled into something thats used to make folinic acid. Folinic acid is used for stuff like building new DNA and other purine-related stuff I still need to really wrap my head around. Then that form of folate is recycled back into 5-mthf. This last step is the one that uses the MTHFR enzyme. Food folate has a combo of both forms. I was supping straight 5-mthf and when I replaced half that with folinic acid, my mood stabilized quite a bit, and some random sneezes stopped. In short, both are better than folic acid, and from there, a safe bet is to use both (I alternate, one one day, the other the next) and maybe play to see what you feel best with.
In terms of brands, 5-mthf is patented, so they're all using the same stuff. Feel free to shop around for the best price or the best combo with other nutrients!