(Can find it in the links post if you have no idea what I'm talking about)
They're all pretty much the same, except for a 1 point or so difference in various stats.
So, in the short term anyway, I won't be getting/levelling Ninja, I see no point.
And if I just use a Mithran scimitar in my offhand forever, I'd be pretty screwed damage-wise. Though the AF Knife is 2 Dex/Agi, that might make a decent offhander.
I'll give it some more thought when I'm higher, when perhaps the stat gap will be larger.