They're very different ships, despite similar hardpoints.
The FAS is an amazing combat ship - it feels like a big Vulture. Despite it having low shields that's rarely a problem in PvE as its armour is amazing. It's a ramming machine - it weighs more than an Anaconda and will come off better ramming one, and small ships just spin off into oblivion without leaving a scratch. It has enough space and power to stack SCB for PvP.
The Clipper has more shields, but its survivability is actually lower. The hardpoint placement means you can't really use fixed (while the FAS can stack rails and plasmas and hit will all of them).
In a fight between the two I'd pick the FAS every time.
However the Clipper is much more versatile. It can be a much better trader, a better miner, and so on. It's too wide to dock at outposts and docking at regular stations is harder, and those really ruin its versatility for me. It does look amazing though, while the FAS looks like a fish had sex with an iron brick.