"Easiest"?
USB floppy on the MacBook Pro.
"Easiest if you have way more files than fit on a single floppy disk"?
SCSI ZIP drive on the LC, USB ZIP drive on the MacBook Pro. This requires more work, because you need TWO drives, one for each system, but it does increase capacity per transfer 70 times.
"Best for arbitrary transfers at random times"?
Ultra-complex multi-computer networking setup, where the two systems don't talk directly to each other; but both talk to a single network share that shares both AppleTalk/AppleShare and Ethernet/NFS. (i.e an AppleShare IP 6.0 Server with AppleShare bridge.) Then you just write them TO the network share from the LC, and grab them FROM the share on the MBP. (Or just use them from the share.)