Most acrylic and water colour paints are not legal cosmetic products and so should not be used on salon clients. Water colour paint nail art, often called Aqua nail art, uses a different technique and generally these paints are not suitable for the type of nail art that most NT want to do.
Acrylic water based paints vary a lot in quality. Arguably one of the best brands is Mai Meri "Polycolour" paints that are favoured by many of the top nail artists when making competition work.
The main issue with acrylic paints for beginners, is that they can dry out before you finish your design. This problem is removed if you use nail art gels as these need to be cured to harden and give you more time to work. However, when making a more complicated design, the process of painting, curing, painting the next item, curing, painting the next item, etc can be tedious.
As a consequence of all of this, many Nail Techs use gel polishes for nail art painting because they have them already and their designs are relatively simple. For detailed work or fine lines, most gel polishes are not sufficiently pigmented (which is why the same brand probably also sells nail art gels).
There is one exception and that is the PRIMA gel polishes developed by my company IKON.IQ Nails. These use a unique pigmentation chemistry that means they only require on colour coat, but that they are also ideal for nail art, including fine detail work and one-stroke.
