The chassis is built for up to a 5-point harness. All of the mounting points are there, one in the seat center, two hip mounts, and the two shoulder mounts to the tube behind the seat.
As far as preference, there will be a lot of opinions here. We elected for the 4-point because Kaleb didn't like the idea of the strap bunching up his nuggets. Me, it doesn't matter anymore. I do find the lap part of the belt tends to ride up on my large frontal girth. I find the 4-point much easier to get in and out for not only me but new riders. The 5-points harness require a 30-minute tutorial for the harness virgins and which can give you that opportunity to get extra close and touch-feely with your favorite passenger friend; that can be a very good thing or a very bad thing.
Obviously, the 5-point will give you more security than the 4-point. The 4-point is easier to get in and out of. You have to decide which is more important. The camlock is very nice, especially to release all five harnesses at once. The 4-point also has only one button to release.
Seat choice can also make a difference on the type you should get.