I went through this last year when I was planning my own big trip. Similar situation here—I was basically obsessed with finding the perfect balance between price and performance. I really looked at the Sony E 16-55mm f/2.8 G because everyone says it's the 'king,' but honestly, that $1,300 price tag is just painful when you're also paying for flights. I just couldn't justify it. In my experience, comparing the Tamron 17-70mm f/2.8 Di III-A VC RXD vs the Sigma 18-50mm f/2.8 DC DN Contemporary for Sony E came down to pure practicality. The Tamron has that sweet extra reach and stabilization, but it's lowkey huge. I ended up with the Sigma cuz it’s basically half the price and so tiny. Since the a6700 has IBIS anyway, I didn't really miss the lens stabilization. Over the years, I've tried many setups, and honestly, the Sigma is just insane value. I saved like $700 which paid for so many meals! So yeah, my lesson was that the 'best' lens is the one that doesn't make ur wallet cry or ur neck hurt after 10 miles of walking... peace

sooo i actually hauled a heavy setup last year and it was lowkey a nightmare. i was so disappointed with how much my neck hurt lol. unfortunately, the Sony E 16-55mm f/2.8 G is just too expensive and heavy for what it is. honestly, just get the Sigma 18-50mm f/2.8 DC DN Contemporary. its like $500 vs $1k+ for the Sony. ur back will thank you and u save money for Japan snacks!! gl!!

Adding my two cents since I've been shooting E-mount for about 6 years now. While everyone loves the Sigma for its size, you really should check out some side-by-side comparisons on RTINGS or the interactive sharpness charts on The Digital Picture. Honestly, if you're doing street photography in Japan, especially at night, that extra reach on the Tamron 17-70mm f/2.8 Di III-A VC RXD is a total lifesaver. The a6700 has IBIS, but combining it with the Tamron's VC stabilization makes a massive difference for steady handheld low-light shots... its basically like having a tripod in your hands. It's definitely bigger than the Sigma, but having that 70mm end means you can grab those tighter compressed street shots that 50mm just misses. If you're looking for reliability and dont want to regret leaving a longer lens at home, it's my top pick. Plus, you can usually find it for around $700 new, which is a way better value than the Sony E 16-55mm f/2.8 G tho.

sooo i totally get the struggle... i was in ur shoes a few months ago after picking up my a6700. honestly i was worried about spending a ton of money on something heavy and then regretting it halfway through the day. i'm still kinda new to this but i really value staying light so i dont get worn out or draw too much attention to my gear. for your trip, i'd highkey recommend the Sigma 18-50mm f/2.8 DC DN Contemporary for Sony E. i've been using it and i'm super happy with how it handles low light for such a tiny thing. the Sony E 16-55mm f/2.8 G is nice but it's expensive and i was scared of bumping it lol. the Tamron 17-70mm f/2.8 Di III-A VC RXD is just way too big for me... felt like a total brick. TL;DR: Grab the Sigma 18-50mm f/2.8 DC DN Contemporary for Sony E because it's tiny, sharp, and wont break ur back during those 20k step days in Japan! gl!