Definitely not an authority on this matter, but the Famicom library is definitely more RPG heacy and since you understand Japanese well, you are at a huge advantage for being able to acquire and understand these titles. There are also a lot of side scrollers, SHMUPs, and other strange titles that were never released outside Japan that are also available to you. In terms of pricing on a lot of them I honestly have no idea, but as you said, most Famicom imports are going to cost you less, especially when compared to their US counterparts if they exist.