there's never a best anything, only what makes sense for you, your needs and your budget.
That's nice, they're nice and long. With the cheap Harbor Freight ones, length is often an issue.^^This. For my limited needs, I get away with these cheap buggers. They were a great upgrade from a shorter set (no more having to care which side the battery is on when I'm parking). They don't take up much room when they're rolled up in the case they come with, and the clamps are decent. The actual wire ain't much, though, so they may take a while to get the job done. If I used them more than a couple times a year, I might shell out for a better set.
If you're looking to jump semi trucks and tugboats, Steve's 4/0 set would be perfect!
Excellent advice from Greg. Heavy gauge, low resistance cable does no good when it is crippled by clamps that add resistance through poor quality and the inability to provide a good connection to the jump contacts....
Stay away from the ones that have the cheap clamps..