Choosing Macro Lens

I stumbled across a post in strobist forum on flickr earlier which somebody asked for advice in choosing macro lens while she had the Tamron 90mm in mind. Just thought I'd cross post my response here since this might benefit others who may be interested in the subject and elaborate a little. Below is my post:

Be advised... all 3 versions of these 90/100/105 versions of macro lens made by Sigma, Tamron, and Tokina are non-internal-focus lenses. You'll notice the barrel moving in and out and takes a little while for the barrel to travel. Focusing with these macro lens even with the built-in focus limiter would be slower than normal lens or the Nikon/Canon internal focus versions. This down side magnifies into a much bigger problem if you're shooting under low light conditions or subjects that's hard to focus because it would take forever for the lens to hunt back and forth to lock the focus. Manual focusing ain't easy either if your subject is in motion.

If you're looking for a special effect lens or want to explore the macro world, you wouldn't be disappointed with the sharpness of all 3 flavors no matter which one you choose. However, keep in mind that the focus speed would pose problems when using them as "walk-around lenses".

Note: I find myself sticking the with 50mm F/1.8 more than whipping out my Sigma 105mm F/2.8 for closeup shots, and almost only use the macro lens for what it's made for - macro.

Frankly, if I were to choose all over again, I might go with the Tokina regardless of image quality 'cause all 3 flavors are extremely sharp. And for the 2 lenses I have purchased with Tokina - 12-24 F/4 and 16-50 F/2.8, I frankly have nothing but praises for them especially with the smooth operation and build quality. But of course, if budget isn't in the equation, I would absolutely go with the Nikon AF-S 105mm IF-ED VR. The added cost goes towards the Nikon quality, great customer service/warranty, internal focus, Silent Wave Motor (SWM), and Vibration Reduction (VR). All these would make the lens MUCH more usable and desirable on the field. But for now, my Sigma 105mm F/2.8 does the job just fine. :)
More on this subject later, and I'll be writing a little more in depth in gear selection next.