There are three kinds of cutterhead:
(1) Basic straight knife. Initial cost is low. Setting the knives is a tedious, time-consuming task that requires the use of dial indicators and/ or jigs. As our regular viewers know, I'm
not a big fan of setting jointer knives
(2) Indexed knife system. There are
lots of variations with different names, but you basically take a straight knife and plop it in without having to worry about setting it at the right height. Slightly more expensive initial cost, knives usually a little more expensive.
(3) Helical head with carbide inserts. Higher initial cost, long life of the cutters. There are no knives to set, you just screw the cutters in place. An additional advantage is that the shearing action of the carbide helps reduce tearout. Overall, the finish is very good, but you may see very slight ridges you won't see with a straight knife system.
For your first jointer, I think Mark has the right advice. Go with a simpler, cheaper model. Because there is a good chance that after you've used it for a while, you wish you had a bigger jointer (8" or even 12"), or a helical head with carbide inserts. Besides, I wouldn't want you to miss out on the joy of setting knives... :rolf: