Could you/Would you

[Itasan]

I wonder which is more polite:
1-1. Could you pass me the salt, please?
1-2. Would you pass me the salt, please?
2-1. I'd appreciate it if you could pass me the salt.
2-2. I'd appreciate it if you would pass me the salt.
Thank you.

[Tdol]

I'd say 'would'.

[Itasan]

Thank you very much, todol.