Experienced both H & S and Iwata.
My experience is and there is more but I will keep it simple John. No disrespect to you.
H & S. For Priming and varnish. Assume we are talking acrylic as I have no experience in enamels.They are both dirty paints and the worst to clean up.
The Evolution is a very nice brush. It breaks down into 6 parts very easily. The nozzle is easy to clean. No spanners are required. For Priming and Varnishing a .4 needle/nozzle
There are also available .0.15, 0.2, .04 and 0.6 needle nozzle alternatives for the same brush.
It is a high performer yet a simple brush. Needles are sold separate from the nozzles. Every part on an H And S brush is replaceable. The cup is removable. There are two sizes of cup available.
The Evolution can be taken apart with the fingers
For closer and intricate work Iwata is better.
Breakdown an Evolution clean all parts put together my record is 4 minutes and that is a clogged up one.
Iwata. For priming and varnish not so good. They will do both these things but I find you need to take the whole brush apart to clean.
OK this is the same as the H & S. However the Iwatas are somewhat better engineered but to take them apart is an absolute pain. A real pain compared to the H & S.
The nozzles are minute and difficult to clean. Most Iwata have matched needle nozzles so a replacement is the whole lot. The body is not replaceable as the Iwata.
Cup are moulded into the main body one size only.
They are more intricate and touchy and not as friendly as an H & S.
But for all top coats and larger detail work I use an Iwata Eclipse HP BS. with a .35 needle/nozzle no alternative sizes.
It is small in length and light with a small low cup which helps when airbrushing especially to get into difficult parts.
It produces a slightly finer paint finish than an H & S.
Breakdown an Iwata and clean a load of bother.
An Iwata HP BH I use for close detailed work and this is available in .2 and a .18.. Still learning.
Spanners are needed to very carefully remove and replace the nozzle.
Those are comparisons but to be remembered that both are great brushes and the differences are close. Please remember this is my personal opinion not one taken from other blurb.
Laurie