Personally? No.
Reasons:
Mamba
is more powerful and fast, but crucially it is rubbish at turning around. Now, when you have split seconds and a foe is dodging over you that can mean killing a mark or having to bug out early.
If you are allowing yourself to be hit, you are doing it wrong in a Clipper- its all about bullying smaller ships, and jumping out fast. At points you'll have about ten seconds to wipe out the target and jump, so really you need to gank the NPC rather than dogfight it.
M pad is nice, but its not a be all / end all thing. I like to plan ahead and anticipate L pad issues- plus, when you are out BGS murdering it does not matter if the victim system has L, M pads.
Lastly: cost. The Clipper is cheap- really cheap. Rebuy and fines are much lower, while the Mamba is costly. Its like going on an attack driving a Bugatti- I'm not Dominic Toretto in Fast and the Furious