I'm happily running El Capitan on my 2015 Macbook.
Only thing tempting me in Mojave is dark mode.
Did anyone upgrade on a 2015 Macbook? What's the speed like?
2012 Retina MacBook Pro. Speed is perfect. No complaints. Dark mode is the bomb. It's like I got a new computer for free.
Most tools I am using are dark mode so having Safari and the desktop and XCode dark mode is absolutely perfect.
For all the technical changes over the years, Dark Mode is the most noticeable upgrade ever. It just looks badass.
As for speed - the thing is Intel hasn't really made their processors significantly faster in the last 6 years. There's some improvements but they're marginal. 6 vs 4 cores would obviously make a difference but other than that - CPU speeds just haven't improved very much.
Look at the detailed benchmark scores of a brand new "high end" 2.9 Core i9 vs. the lowest end Intel i7 6 core processor - very different prices, and 2.3 vs 2.9 Ghz sounds like a big difference, but the actual speed difference in the benchmarks is something like 10%, if that. Both processors have turbo boost etc so they don't actually run at those frequencies. They run in a thermal envelope taking into account speed, power use, and heat. In the end they're nearly the same.
I think the lower spec ones are just made to sound worse for marketing reasons, and the higher end ones are made to sound better, but it's really pretty much almost the same thing, for a $700 price difference...