I'm no expert but if I had to move data files from one machine to another, I would use a USB stick or external USB connected Hard disk. Currently, I have a few 8 GB sticks laying around. Would use it.
But if more then 30 Gigs of data, I would buy an external Hard disk. After moving the files over to the new Mac (via USB connection), I would then configure that USB external Hard Disk to be a backup storage device. Using Time Machine, I would backup up the data files I wanted. Thus, win-win in the long run.
Buying an external Hard Disk is expensive (re: $100 or so) but in the long run (as an attached backup storage device), its well worth it...
Good luck
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