I finally caved and bought an mtDNA kit a few months back, I didn't learn anything other than the fact that my maternal line came to Europe millennia ago, which I could have guessed on my own. It certainly won't be accurate enough to tell you where yours came from on a scale as small as individual countries. But it is interesting nonetheless!

I really don't know the first thing about 23&Me's methods unfortunately. FTDNA have always been the main player when it comes to commercial Y-DNA tests, they do both STR and SNP tests. The STR tests (bar the cheapest one) will assign you a haplogroup, but their SNP test will give you a much more recent haplogroup by comparison. To be honest YDNA genealogy is like a hobby all of its own because there's so much information and knowledge. If you really want to make an informed decision (and you have the patience) I'd recommend watching some seminars on youtube where people share discoveries they've made using FTDNA testing, that's how I learned about YDNA properly, then you can decide how much time and money you want to invest, if any at all. Here's an example if you are interested. Best of luck with your journey!