Alright, so as some of you have noticed, I recently posted a Tamron 17-50 f/2.8 and Sigma 18-50 f/2.8 Macro for sale. Funny thing is, within minutes, I received around 5 PM's asking me which one I liked better and why.. etc etc. So I figured I would give some of my thoughts on both lenses.. although I'm not a professional photog, I do like to think of myself as more than an amateur or total noob. So hopefully my opinion counts for something and maybe it'll help you with your lens choice. So here goes nothing...
Pro and Con's of Tamron 17-50 f/2.8
Pro: Super SHARP when focus is spot on.
Pro: Wide 17mm is useful for landscape to walkaround shots.
Pro: Retains resale value pretty well
Pro: Focuses better in low light? (Really subjective, I could be completely off)
Con: Noisy focusing mechanism.
Con: Sub-par build quality compared to Sigma (but still good).
Con: Zoom's opposite of Canon and Sigma lenses (may take time to get used to)
Pro and Con's of Sigma 18-50 f/2.8
Pro: Focusing motor is a lot more tolerable than Tamron IMO.
Pro: Better build quality than Tamron (love that EX finish)
Pro: Can do macro or at least can focus a lot closer than Tamron.
Pro: Cheaper.
Pro: Almost as sharp as Tamron (really indistinguishable unless you pixel peep)
Pro: Zoom's same way as Canon lenses.
Con: Not as sharp?
Con: Sometimes focusing isn't as accurate (but hardly noticeable and maybe it's just my copy)... something I just thought about but don't have actual proof so... yea.
Con: Doesn't keep it's resale value as well?
SO THE VERDICT IS: I chooose...........
BOTH! Actually for me, I really couldn't decide which one to keep so I ended up putting both for auction and the one that didn't sell first would be the one that I would keep lol. See... even after I've owned both, I still couldn't decide which one to keep.
Remember, don't believe everything I wrote down for the comparisons. I am no way close to a professional but this is just my opinion from owning both. Hope that helps. Enjoy debating which one to get Don't stress out too much. Both are top notch lenses.
- David