The cutterhead you pictured in your question is a Byrd Shelix cutterhead, which produces a shearing helical cut using square, 4-sided carbide inserts. There are also other configurations of segmented cutterheads with carbide inserts which produce cuts of varying quality.
Contrary to popular belief, helical cutterheads--even the widely-acclaimed Byrd Shelix cutterheads--do not produce perfectly smooth cuts. In fact, the surface is ever-so-slightly scalloped, as you will see if you rub chalk on it or apply finish without sanding first. However, it is easy to remove the scallops by sanding, using a card scraper, or with a light pass of hand planing.
Typically these are referred to as straight-knife cutterheads, but there are also some machines on the market that have long helical knives which run the entire length of the cutterhead. I would consider those machines more similar to straight-knife cutterheads than segmented helical cutterheads.
- Less expensive up-front
- On many machines, knives can be resharpened several times before replacement.
- On many machines, you can eliminate nick tracks by shifting one or more knives side-to-side so the nicks are staggered.
- On machines with disposable knives, it's easy to replace the knives and you don't have to reset the height because the knives are indexed.
- Often produce a slightly cleaner cut than segmented cutterheads on straight-grained wood.
- Less demanding on motor
- Produces tearout in figured wood
- Can be more expensive to maintain long-term.
- Knives can be difficult to set properly.
- If you trash your knives, you need to buy a whole new set.
There are numerous configurations of segmented cutterheads, from 2-sided segmented knives to 2- or 4-sided square inserts. In addition to the cutter configuration, there are multiple cutter placement/alignment configurations. Byrd's cutter inserts are skewed to follow the helical alignment, producing a shearing cut; and the edges are slightly rounded to prevent gouging due to the cutting/skew angle. Other cutterhead designs align the cutters in either a helical or V arrangement, but typically the entire edge of each cutter slams into the wood at once (as with a straight-knife design), rather than producing a shearing cut.
- Produces less tearout in figured wood
- Cutters are easy to rotate or replace
- You can usually (always?) rotate the each cutter at least once before needing to replace it
- Cutters index directly in place and don't need to be fine-tuned
- Inserts are often carbide and last as much as 10x longer than steel inserts
- If you trash the cutters (e.g., by hitting a nail), at worst you probably just need to replace the ones that were damaged; you don't need to replace all of them
- Square-insert segmented heads produce a slightly scalloped surface (though they are easy to remove with light sanding, and some configurations are worse than others)
- More expensive up front
- More demanding on motor
Contrary to conventional Internet wisdom, side-by-side comparisons have found helical heads to be more demanding on the motor. In the tests, machine fitted with a helical head drew more amperage than an identical machine fitted with a straight-knife cutterhead. The current explanation for this is that a cutter is always engaged with the material, producing a constant load on the motor.
According to Bob Hunter of WOOD Magazine, upgrading a benchtop planer to a segmented cutterhead is an iffy proposition for two reasons: (1) the motor may not be up to the task, and (2) segmented cutterheads produce better results with a larger cutterhead diameter than what is available in a benchtop machine.