Cartridges were probably pretty fast to load, but I don't expect that Commodore's floppy drives were particularly fast, even if they were much faster than cassette tape.
Not sure about the commodore but atari's floppy drive was connected via a 19200 bps serial connection so even for those days it was really slow.
Both atari 8 bit and commodore had a disk drive with a trimmed down 6502 in it so you basically bought a second computer. This is why the drives cost more than the computer itself.
I was an Apple ][ (well, Franklin Ace, technically) guy back in the day, but my high school used mostly C64s. The slow speed of Commodore floppies infuriated me. And they even had their own CPU inside the drive! By all rights, they should have been faster than Apple drives which were run by the computer's CPU.
