This debate continues to rage in many foreign-based detailing forums. Both are excellent products, and both have their respective followers. I thought it might be interesting if I can post my opinions from a Msian perspective, since our climate is so different. These opinions are based on more than 8years usage and experimentation of both products and are 100% unrelated to any foreign forums+websites comments and advertising talks. These are my opinions, and I am sure many Z and K users may hv different opinions. My intention is to share mine with others, and not to challenge any users, discredit or praise any brands. SUITABILITYZ and K performs optimally on:1. Any new OEM paint that's swirl free.2. Any professionally-sprayed aftermarket paint jobs that's free from any blurness or other defects. If you hv swirls, all kinds of stains, watermarks, blurness due to lousy re-spray job etc etc, Z and K cannot help you. SURFACE PREPZ and K cannot correct serious defects. Z and K magnify any swirls. Z and K should be used, and performs optimally on well-compound surfaces that are 100% defect free. Look at the Z cars posted on the websites...all of them are enthusiast vehicles with good paint that's well prepped. If surface is sanded and compounded first, and you use Z and K, the results are marvelous. GLOSSZ and K will not change your colour in any way unlike waxes that often darken the colour slightly,leading to adjectives such as "richen, deepen, warmer, radiance, glow etc". Z and K actually increase the perceived brightness/reflectiveness of your clearcoat, making you say it's glossy. The look is similar to having a layer of clear plastic skin on your paintwork. Some say it's akin to a 2nd clearcoat. Zaino has a slight edge in terms of clarity. The brightness looks clearer, more wateryJust imagine a 100% clear plastic wrap vs 90% clear plastic wrap. To many people, Klasse is already impressive, but upon very close scrutiny and side-by-side comparison, Zaino has that slight edge. DURABILITYIMO, Z and K shd not be assessed via water-beads. The Klasse and Zaino look lasts about 3mths. Cars were parked outside in the day, indoors at night, and washed twice a week. No quick-detailers usedOf course, this is also due to the excellent surface prep of the paintfinish. WATER-BEADINGFor enthusiasts who love water beads:Klasse: Dissappointing. Beads will weaken after 2nd week. It will start sheeting water. Zaino: Very small beads for 3-4 weeks. After that, looks like everything is gone. Looks is still there. APPLICATIONZaino:Once you start Z, you'll be stuck to the Z system since you can't mix with other brands. Other spoos contain wax, which hinders the layering process that is critical to Z's results. Using Z takes a lot of knowledge, reading and considerable time-management before doing the 1st time.People who don't understand often mis-use Z and complain. Klasse:Klasse AIO is very easy to use. Klasse HGSG could be difficult if you don't know how. Once you've learnt the trick...wallaaaa!!!Some foreign application methods, reported to be effective, may cause problems. Every Klasse HGSG user might hv their own style. I hv mine too! SUMMARY:Zaino:Truly excellent product if you hv a well-compounded, optimal paint finish paint that's 100% swirl free. On Msian cars, sadly, lots of surface prep must be done (including maybe sanding!!) before you can reach this stage. To be layerable, your car must be washed at least 3 times a week so that it's clean enough to accept further layers. If it's stained and rough, layering is impossible. The Zaino life is for the dedicated, hardcore enthusiast who understands the system, and who can spend time to do layering. If you want the ultimate wetlook and don't mind the amount of work involved (surface prep + 1st application), this is for you. Klasse:Truly excellent product if you hv a well-compounded, optimal paint finish paint that's 100% swirl free. On Msian cars, sadly, lots of surface prep must be done (including maybe sanding!!) before you can reach this stage. To be layerable, your car must be washed at least 3 times a week so that it's clean enough to accept further layers. If it's stained and rough, layering is impossible. Especially effective on silver and light coloured cars, and the result is very, very close to Zaino. These 2 brands are not something any ah kao can just buy and blindly apply to their aged cars.Lots of prep work needed to enable these 2 brands to show off their optimum prowess. Note: The above are my summarised opinions, without going into much technical details.