Migration Assistant or Time Machine backup. I forget which I used when I transferred to my latest machine (probably TM), but whichever one you use, use the fastest connection possible. For MA, that's probably ethernet (wonder if it now supports USB3 or direct Thunderbolt). For TM, use a direct drive connection (probably USB). I don't have one, but I think if you use a Time Capsule, you can temporarily connect it directly to your new machine to speed up the transfer. Basically, avoid a migration over wifi. It will take a really long time.
Steve