I will add my .02 by first saying that I have an 11 year old 15" planer and an 8 year old 12" jointer with Byrd Shelix cutterheads and have not yet needed to turn the cutters. That says that I should get at least 40 years from a set of cutters since they can be rotated 4 times. I guess I won't have to worry about that at 74 yo. Lol.
I never pay attention to grain direction when milling material because I know there will not be any tearout.
With straight knives, whether 3,4 or 50, it is required to hold the board down onto the table because of the "chopping" action. With the Bryd Shelix shearing action the board is actually pulled down to the table. I have demonstrated this many times to shop visitors and they are amazed. (Obviously, I do hold the board down for control purposes).
As far as "tracks" or "grooves", if there are any that are really noticeable then there is something wrong with the setup.
In an earlier post .001" deep grooves were shown. 2 swiped with a ROS and 180 grit sandpaper and they are gone. I have never applied a finish to any material straight from a planer/jointer without sanding first.
I feel that the Byrd Shelix design is so great that they should come standard on all machines.
As for spiral, helical, shelix, etc. controversy, the following attachments are info from Sheartak Tools Ltd who make all types of cutterheads, so I think they have an idea on what is what:
Again, just my .02, but I will never own another straight knife machine.