There is really no such thing as a Gigabit Ethernet cable. There is CAT 5E which is 1gig and there is CAT 6 which is capable of 10gig. Thunderbolt is also 10gig.
Which Thunderbolt 1 or 2? I assume the following was TB1.
"I recently did some experimenting with the migration assistant. The source machine is a 2011 MacBook Air and the target machine is a 2012 Macbook Pro Retina. The data transferred is 127gb.