The longer the transmission, the greater the loss of connectivity counts for pretty much everything.
As long as you don't plan to connect your ethernet cable from your modem at home to your neighbour's PS3 down the road that loss will be ignorable as far as I know.
For wireless, the loss will be greater as the distance increases and is affected by what stands between your modem and PS3. It would be wise to keep chicken wire fences away of the path (but do encase your house in it, that way your neighbours will get a horrible if any connection from your router so that spares you the trouble of protecting it with a password)
You should be perfectly able to get a decent connectivity from either means.
Do mind that both my PSP and PS3 have this strange thing going on with my router.
When upstairs (modem is downstairs), a few centimetres can mean the difference between a connection of 95% and 20%, I believe a cable would be best for a PS3 since you won't have to rely on your PS3's wireless receiver that way.
But my not too young house has massive walls filled with cables, I hear America has a thing for thin instant-destroyed-by-hurricane walls so that shouldn't be a problem even if you have a wireless internet.