I've levelled both SMN and NIN to 50 and I prefer SMN, I'm biased though as SMN was my first job, but I also find the Mudra lag to be annoying and has screwed up my rotation more than once.. also, ignore Akiza, she's been slamming SMN for months and will take any opportunity to tell you why x, y or z is better than it. As others have pointed out though the expansion is coming out soon and it'll turn most classes and any tiers people have created on their heads, so just go with what you find the most fun.