you know that people are going to have a hard time answering that one...lol.
If you put a gun to my head I would probably go with Malabrigo. I love the colors, the cost is pretty good for the yardage, and it is delightfully soft (even better knit up!) and i found it felts great!
I love koigu because it has an outstanding color palette!
BUT! If Misti Alpaca had more colors or more vibrant colors that i absolutely loved, it would be that yarn every single time. It seriously makes me hate my malabrigo for a bit after I use it because it is soooooo soft. it is more expensive than i will usually spend but i do love splurging on this stuff...they just need more bright colors!