That depends on who you ask.
If you ask an International style dancer (and Quickstep is, after all, exclusively an International style dance), they'll tell you that Quickstep is one of the easier dances... certainly easier than Slow Foxtrot. It takes more control to really dance SlowFox in a flowing and musical way.
On the other hand, if you're comparing Qstep to American style Bronze Foxtrot, then Quickstep might be considered more difficult... although not by much. You'd think the speed would make it more difficult, but it really doesn't. The difficulty is simply in the syllabus itself; Quickstep has more challenging figures.
Yes, the Quikstep is bright and upbeat, with more release and flight than Foxtrot. It's fun... I highly suggest giving it a try!
Sincerely,
Jonathan Atkinson