Im stressing out because I have a big trip to Japan in three weeks and my kit lens just isnt cutting it anymore for my A7III. I really need one solid lens that can handle street photography and maybe some portraits without me constantly swapping glass. Ive been looking at the Sony 24-70mm f2.8 GM ii but damn that price tag is scary, and I saw some people online swearing by the Sigma 28-70mm f2.8 instead since its way cheaper. Is the GM worth the extra grand or am I just paying for the badge? I dont want to regret my decision when I get there so what is the best all-around lens for someone like me?
I totally get the sticker shock. I spent ages debating the same thing before a trip to Osaka a couple years ago. I ended up grabbing the Sigma 28-70mm f2.8 DG DN Contemporary and honestly, I never once felt like I was missing out because of a badge. It is so light compared to the GM version, which matters when you are walking 20k steps a day in the humidity. My back was so happy I chose the lighter setup. The images look sharp enough for any print I wanted to make, and it fits in a small sling bag easily. Just keep in mind that 28mm is a bit tight for some of those narrow shrines, maybe pack a cheap manual prime if you really need wider shots. Save that extra grand for some incredible sushi instead, seriously.
Regarding what #2 said about the sticker shock, they are spot on. I have analyzed the MTF charts for both the Sony FE 24-70mm f/2.8 GM II and the Sigma 28-70mm f/2.8 DG DN Contemporary and the performance difference is negligible for typical street travel shots. You are basically paying for an extra millimeter on the wide end and slightly better weather sealing with the Sony. If you want to keep your budget intact, the Sigma is definitely the better investment. I honestly think you should put that extra thousand towards a nice Tamron 70-180mm f/2.8 Di III VXD if you find yourself needing reach, or just treat yourself to some amazing food in Tokyo. The Sigma is plenty sharp, works well in low light, and you wont be stressed about damaging a massive lens while walking through crowded markets.
Honestly, Japan is a once in a lifetime trip so dont stress yourself out over gear specs too much. I have been shooting Sony mirrorless for a long time now and have dragged way too much glass through Tokyo and Kyoto. In my experience, dragging a heavy bag around those narrow streets will kill your vibe faster than any minor sharpness difference between lenses. If you want my advice, keep it simple. You really dont need to drop that much cash on the top-tier professional glass just to get nice travel photos. I have tried many setups over the years and found that a versatile zoom from Sigma is actually totally fine for what you are describing. People get obsessed with the brand badges but honestly the newer third-party options are just solid workhorses. You get that constant aperture and it basically does everything you need for street shots and portraits without breaking your back. Just go with a standard zoom range from Sigma and you wont have to worry about swapping lenses when you should be enjoying the sushi or the shrines. Save the extra money for better food or experiences while you are out there. Trust me, you are gonna be way happier having a lighter setup when you are walking ten miles a day.
Just wanted to say thanks for everyone chiming in. Super helpful discussion.