My browser upgrade path is all over the place and largely dependent on the type of Mac I was/am using. So, rather than give a detailed list I will simply say that I prefer customization over speed. I am willing to sacrifice some amount of speed for the ability to make the browser be and look the way I want it to. Because I generally spend about 16 or more hours a day in front of a computer. I want to be comfortable in my browser.
Right now, my main one is Vivaldi. Vivaldi is by some of the same people who did Opera. It uses the Chrome engine, but because it has Opera's influence I can do things like have my address bar, bookmark bar and tabs at the bottom instead of at the top. And Vivaldi, because it's based on Chrome, can install all the same addons that Chrome itself uses. I get customization and access to addons.
As to why I kept the 11PM, well…upgrades for us (my wife and I) are usually every 3.5 to 5.5 years. We upgraded in 2021 but for cost reasons and network reasons I went with the 11PM (brand new) instead of waiting for the launch of the 13 series. It was cheaper monthly.
Network wise, I've been a guinea pig on Sprint when Sprint launched LTE. For a couple years my iPhone 5, an LTE device, only got 3G. And I had to deal with all the issues Sprint had with Network Vision (their LTE rollout). At the time I got the 11PM, T-Mobile was solidly pushing out it's 5G network. Having experienced what I experienced with Sprint, I had no desire to repeat my performance as a network guinea pig with T-Mob's 5G rollout. So, the 11PM being LTE only I'm doing just fine.
Also, I have a T-Mobile issued femtocell at home for connectivity reasons (without it the coverage stinks at home). It's 4G/LTE only so at home with a 5G device I'd be at the mercy of T-Mobile's 5G network. Of course, I could have a 12 or newer device just switch down to LTE only, but then I'd have to remember to switch it back when leaving the house. No, all the way around I chose to simply wait until T-Mob's 5G network has worked out all it's issues. By the time I get the 15PM (when the 17 series launches) 5G will be old hat (or SHOULD be).