I've wanted to ask this for a while but feared it might just turn into another men v women argument , so I hope it doesn't .

when I think back over the various cats we've had and others I've known the girl cats do seem to have been smarter , one girl cat we had used to wee in the loo and knock the door with the knocker .

the boy cats always make the mistake of begging for food whereas the girls would never dream of asking , they always simply fixed me with a 'Headmistress' stare and I'd go and get the food immediately .

the girls seem to think more about things , the boys more prone to just rush at something .

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Sounds like humans not cats!

Since the girls have to bring up the kittens single-handedly I'd expect them to be more resourceful.
I've only known two cats though - my current girl can be quite bright whilst our old family cat was a half siamese ginger tom who was also pretty clever so I can't bring any evidence to the thread.

No, male and female cats can both be dense. Blaze is like action cat, doesn't think things through all that much, and she has a habit of getting into places she can just about squeeze into, then panics when she realises she can't back up or turn around and get out. She got stuck behind the washing machine the other week which was a bloody nightmare to pull out. Her sister, Sphynx, usually just waits and watches to see whether Blaze gets into trouble (either hurt or getting told off) before she follows about an hour later.

When they were kittens they both decided to climb up a fabric wardrobe and stand there gobbing off, knowing that daddy would get them down, except one day I didn't. I spent half an hour with them acting all feeble, trying to coax them down and when they finally realised it wasn't happening Blaze came and sat at the edge for one last attempt at cuteness. I noticed Sphynx looking at her like she was working something out before she actually pushed Blaze over the edge (she actually put both her front paws on Blaze's back and shoved) to see whether it was possible to land without injury. Blaze didn't take too kindly to this and shot back up the wardrobe only for Sphynx to knock her off a second time. This seemed to assure Sphynx that landing safely was possible and she came down of her own volition.

Sphynx also seems to be the one that has mastered a sort of language to communicate. It sounds like she's making an attempts to actually vocalise certain words like "food", "treats", "fuss", etc to say what she wants. It's not just she has a certain miaows, it actually sounds like she's trying to use words. She is quite a gobby cat anyway, and when my wife or I come home you get about ten minutes of her sitting in front of you while she tells you what's happened beyond the invisible force field all day. I swear one day I came home and went "Hello you two" when I was greeted at the door and it sounded like Sphynx actually went "Hi!".

I've had both and I've not noticed any difference.

Girl cats stay closer to home, and don't wander off for long periods, so in that sense they act a bit brighter, perhaps.

Yes queens tend to last longer than toms (who are more vulnerable to be run-over because of their wandering tendency). I've had 3 toms and two queens. The toms lasted an average of about 5 years (2 killed by cars), my current queen is 18 and my last one passed away at 24, sunbathing in the garden!