18-105 is very comparable. I would think the biggest disadvantage of the 18-105 lens is on the wide side - I think there is a notable difference between 16 vs. 18. I hear and believe that the wide side of the 18-105 has more distortion. The plastic mount doesn't bother me at all, and I have not heard of anyone actually having any problems with this mount. I think it's mostly a perception, maybe even a little bit of a snob thing that it needs to be metal. I can actually think of one advantage of the plastic mount (wear). The 18-105 is also a lot cheaper.