Struggling here... my logic was the Sigma 18-50 since its tiny but it has no stabilization and my hands shake. Then I saw the Sony 18-135 has reach but that f/3.5-5.6 is scary for my Japan trip next month.
I have $800 and just need one lens... is the Tamron 17-70 too big?
I went through this exact dilemma before my Kyoto trip last year. I ended up picking the Tamron 17-70mm f/2.8 Di III-A VC RXD because that f/2.8 constant aperture is non-negotiable for those narrow, dim alleyways at night. My hands arent the steadiest either, and even with the a6700's IBIS, the lens-based VC stabilization adds a layer of safety at the 70mm mark. It weighs 525g which is heavier than the Sigma, but the trade-off for reach and stability is worth it. Specs that matter for your trip:
The a6700 IBIS is incredible, so grab this:
Like someone mentioned, f/2.8 is nice, but I actually prefer native glass for reliability!