At my last workplace, the OSX laptops were all 2-3+ years old... and were all incredibly slow. I was always surprised that people could get any work done on them. One woman had an OSX laptop that would boot up with the entire 4GB of memory in use, with no applications or agents loaded except maybe spotify. All the shiny UI in the world doesn't make you more productive when you have to wait for a mouse click to register.
The linux machines were whiteboxes of the same age, and while there was a curl or two in setting them up, were still just as speedy and usable when aged as they were when new.
I have a Macbook Pro with 4GB RAM & normal HDD and I don't recommend upgrading past Mountain Lion, since Mavericks uses at least 3GB after booting up. I'm guessing Apple engineers are provided with Mac Pro with blazing speeds so they don't understand the pain of using the latest OSX with 4GB RAM & normal HDD.
As for Spotify, it consumes a lot of memory. You'd better off with iTunes.
The linux machines were whiteboxes of the same age, and while there was a curl or two in setting them up, were still just as speedy and usable when aged as they were when new.