The window management and dolphin for file management for one. KDE let's you easily pin windows on top, show on all desktops etc .. Dolphin gives you a nice multi tab, split pane file manager along with a terminal that follows you along.
On my work macbook - I can't install third-party software and the default window management is just not there. It has problems restoring windows to correct size when i switch external monitors... The experience just isn't as nice as KDE on my home laptop.
I had to install inputactions to get mac like touchpad gestures on my home kde set up but after that it just feels nicer and smoother than my office mac