You should be able to do both with out and speed differences. I have used a longer phone line and used a longer Ethernet cable and both work just fine. You shouldn't notice any changes.
Right now, I have my desktop using a wireless card. I do notice a speed drop when using wireless instead of the wired connection. For some reason, my apartment complex puts the DSL router in the closet in a metal breaker box panel in the wall, so I can't use wired connection any more. I would move it, but the router also feeds the cable, so that is the only place for the cable connections. I'm not sure why they decided to place it there, I can tell a big difference in speed and reliability.