Which linux distro is a matter of trying which works best for you...
But the thing that makes linux different... or slower... is the Window Manager. KDE is nice; Gnome 2 (now known as MAME) was alright, but is outdated; Gnome 3 is wicked, but requires a proper hardware; cinnamon is built on top of Gnome 3 and may be very pretty, but can become sluggish (used to take over 25% of my CPU - a pentium 4 - , if I had over 5 windows open and not minimized).
But the thing that makes linux different... or slower... is the Window Manager. KDE is nice; Gnome 2 (now known as MAME) was alright, but is outdated; Gnome 3 is wicked, but requires a proper hardware; cinnamon is built on top of Gnome 3 and may be very pretty, but can become sluggish (used to take over 25% of my CPU - a pentium 4 - , if I had over 5 windows open and not minimized).