I been told that Finalmouse ULX has superb battery life, easily 10 days+ on 1000Hz polling. The small version is one of the lightest on the market and because its smaller its more structurally sound thus doesn't bend like the large ones. Another drop coming on Sunday.
I second this. Am using the small one now. It's even lighter and better than Medium Batch 1.5 that I also have.
In general, I love it because of the Internet Browser based UI as opposed to having to install a software on my PC like with Razer. My Razer Vipers never failed me for years. But the Razer software tends to crap out once in a while causing lighting issues with the keyboard and mouse.
I'm now starting to appreciate not having lights on my mouse when watching videos. So the Finalmouse UltralightX (ULX) which is just drop dead gorgeous with the Black Panther black design and the gold accents and the no software approach is a lot more suitable for me.
Along with that, it is one of the lowest latency mice out there and the sensor have been smooth throughout.
So I would highly recommend the Medium Batch 2 onwards or the Small. My aim got better with the small vs the Medium. So that is why I'll go with that. But your mileage may vary. I have all 3 sizes just to see which suits me better.
Once you have a mice this light, you won't be eager to change to any other mice for a while. It's the lightest in the market that is hard to match in terms of looks and performance. So it'll be a long while till we see something else that beats it. Enjoy!
TLDR Features:
USB-C Charging and Wired Cable
1000Hz to 4000Hz Polling Rate (8K Polling Rate coming soon)
Lowest Latency
Lowest Weight
High Performance