I've done both, and to be honest, FamilyTreeDNA seems more comprehensive to me.
The genealogical data is one of the main things I'm looking for; 23AndMe has been "OK" and AncestryDNA has just been a waste.
I'm wondering if it would be worthwhile to pay for a data import onto FTDNA.
I've done both, and to be honest, FamilyTreeDNA seems more comprehensive to me.