Just another note on M21 and NXT...
Generally speaking professional detailers tend to use products from the professional side of the industry not the consumer side of the industry. One reason for this is perception by their customers. The thought process goes like this, when a detailer is creating their magic on a customer's car there's a more powerful perception on the part of their customer if they see the detailer using professional grade products, not the same stuff the customer either already has in their garage or sees at the local auto parts store or some place like Walmart.
Does that make sense?
If a customer sees the detailer using Turtle Wax on their baby there's a part of their thought process that says, "heck I could do this". So there's no perception of exclusive, or premium products being used on their car. So most pro detailers trend towards professional products for this reason as well a a jillion other reasons like buying in bulk sizes and of course higher quality products and more niche products that are specifically formulated for dedicated procedures.
With all the above in mind, a pro detailer using Meguiar's would usually choose M21 over NXT if they like the results these product give because the M21 is in the Professional Line and thus give the perception to the average Joe Consumer that the detailer is using exclusive, premium product on their baby.
Make sense?
Now here's my twist on the above; when I detail a customer's car with Meguiar's, instead of using M21 I would use NXT and the reason for this is because after I'm done I want my customer to be able to continue maintaining their car and I know they can find NXT but unless they know what a PBE store is they won't be able to find M21 and you always want to make it easy on your customer to do something, not difficult.
Of course now that I'm here at Autogeek I can simply leave my Autogeek business card with them as it has our online store website address on the front and I can write the name of what they need to order on the back, and best of all we carry just about everything!
Anyway, just a little twist why some people might choose one product over the other.
p.s.
There's two types of auto parts stores here in the U.S.A, not sure how they do things in other countries.
PBE Store = Paint, Body & Equipment. This is an auto parts store that caters to the body shop industry. You can still buy all the auto parts you would find at a Hard Parts store like a starter motor or spark plugs, but in the back room they have isles of paints and solvents and usually a guy generically called the paint mixer.
Hard Parts Store = This would be your normal auto parts store, for example Autozone, Kragen, Pep Boys, etc. These carry everything car related but they don't cater to the body shop industry and don't have a section of the store dedicated to paint supplies and body shop supplies for your local body shops.