I find x86 much more fun than 6502, for various reasons. It is much more common and what most computers run today. If you want to accelerate some application using SIMD instructions, you can actually do this. If you want to write a bootloader, you can do this. If you want to look at the disassembly of your favourite program.
Besides, I wouldn't say x86 is harder than 6502. You don't really 'learn' an assembly language anyway. You learn the most common instructions (loads, saves, arithmetic, branches and tests) and get a feeling for what kind of instructions there are. Now when you write something you use a reference and look up necessary instructions and look for new ones that might be useful.
There were few enough instructions in 6502 that you really could memorize them all (I did back in the day). That really isn't possible with a huge instruction set like in X86. Yes, as you say, you can look them up, but that's no fun.
Besides, I wouldn't say x86 is harder than 6502. You don't really 'learn' an assembly language anyway. You learn the most common instructions (loads, saves, arithmetic, branches and tests) and get a feeling for what kind of instructions there are. Now when you write something you use a reference and look up necessary instructions and look for new ones that might be useful.