I have seen every kind of article claiming that A1298C mutations have more tendency towards neurotransmitter imbalance than C677T, Also, that C677T mutations are more likely to lead to high homocysteine. But as far as I can tell, this started with someone making some kind of conclusion, and then the rest of the internet echoing that same conclusion back to them without bothering to actually do the research.
As far as the research I have seen, the thing that matters is how compromised your MTHFR enzyme is, in combination with how much active folate you're getting. As more research is completed this idea might be refined, revised, or even overturned completely, but for now, this is it.
Of course, someone might have a compelling argument why I'm wrong and honestly, I would love to hear it, and even more, I"d love to see the research!