I have only seen this used by a reputable chef on a Youtube channel I watch and wondered how good these are if its a good investment?
Doesn't matter if it's Gordon Ramsay himself, being a chef doesn't make you an expert on sharpening blades. Many chefs still make use of a sharpening service, especially those who don't have the time to do it themselves.
Any kind of pull-through sharpener is generally pretty ****. Anything that claims, guarantees or otherwise asserts edge sharpness within seconds will generally not give an especially durable edge and usually not that sharp, either.
Whetstones are among the best methods, but take time to perfect and certain stones need a fair bit of maintenance.
Rolling sharpeners are limited on angle and can often wobble around or come right out of place. They're also way overpriced, IMO.
Powered professional kit, like the WorkSharp & Ken Onion series are the quickest, so long as you spend the short amount of time required to learn how to do it properly.
Guided angle sharpeners, IMO, are the easiest to use and ultimately offer the best edge, due to the consistency of angle and time gently taken... but they do also take a bit of time to sharpen up properly.
The biggest factor in a guided system is usually brand - Lansky used to be the leading brand, but they were never the best and their quality sems to have gone downhill.
I personally prefer the WorkSharp Precision Adjust for the diamond stones (ie the same type I use to get chisels and plane blades shaving-sharp), but also because it's only about £60. The Elite version is better and, if you can afford it, the Professional is well worth it.
There are more expensive versions, of course, and other options. Another decent cheap option is a set of sharpening rods (usually sets include both stone and ceramic honing) that are held upright in a block, at various angles, You then just stroke the blade down them and, so long as you are careful to hold the blade as perfectly upright as you can, they give pretty decent results. These are probably the best portable sharpening solution.