For me it's the other way round, i've been trying to use Firefox but the "pinch to zoom" feature in Safari is so smooth, and so crappy in Firefox, that i always keep coming back to Safari...
If you read a lot of text on a Macbook, being able to zoom quickly and efficiently becomes a high priority.
Things like this are much more important for me than energy-efficiency.
I use the text reader built into the OS, due to my Dyslexia, so I guess I never noticed :) For me it's just highlight and press the key to have the test read to me, I have "Samantha" cranked all the way to the top speed. That said, Chrome also has very nice pinch to zoom nowadays.
You may want to get a checkup from an optometrist. No joke. I think almost everyone is affected by age-related degeneration of their vision at some point or another.
Well coincidentally i've been to an optometrist in a hospital about a year ago, my eyes are perfect (i don't have glasses.)
If i open https://news.ycombinator.com/news on my Macbook pro retina 15" i see news items 1 to 22 in a tiny font.. so i zoom to about 10 items which i find much easier to read (bigger text and less info), and using pinch to zoom you can do it very easily - in Safari.
Things like this are much more important for me than energy-efficiency.