Share some boar hair detailing brush products here & my observation.
(1)

Left = Envy Brush (largest size), bought from Singapore (import from UK), after conversion RM13.00/unit (exclude shipment & GST). It mimics the Swissvax style wheel brush.
Right = Braun Brush A7D 1.25" round brush, bought from Hong Kong (import from USA), after conversion RM62/unit (exclude shipment). It is part of the Wheel Woolies (WW) series of product by Braun Automotive.
By comparison you can see the Envy brush boom is slightly shorter. The bristles length of Envy brush is also shorter.
(2)

It is apparent that the Envy Brush has smaller bristles brushing area. It also can be seen that the Envy brush bristle density is not as high as the A7D. i.e. for a same unit area the A7D has more number of bristle compare to Envy Brush.
(3)

In this photo I try to push away the bristles of Envy Brush to reveal the center. There is a wood put in the center, hence at the center there is actually no bristle. The bristle is only located at the circumference. In constrast, A7D has full bristles coverage even in the center.
In term of
(a) Bristle softness
Both are equal softness. Comparable to the softness of a brand new wood paint nylon brush. Definitely safe on delicate surfaces.
(b) Built Quality
No doubt A7D is much better by a lot of grade. Having a longer bristle also enable the A7D to be slightly softer than Envy Brush.
(c ) Chances of bristles falling away
Upon purchase both brushes already demonstrate few bristles falling away from the holder when lightly pulled by fingers. So in this aspect both are equal. It also means that one is unrealistic to expect this kind of brush will last forever. Eventually the day will come when there is enough bristles has gone and too little bristles left to do the cleaning job effectively.
(d) Safety Factor
Both are equally safe because there is absolutely no metal parts outside. There is only plastic. Which is also a reason I like to use this kind of brush in case I accidentally bang into the paint with the brush or drop it onto the panel, I knew they will not be deep scratch. And it will not rust (unlike wood paint brush wrapped in plastic cover). Nevertheless, having no metal component holding the bristles could be a reason why the bristles are easier to fall off from the holder compare to normal wood paint brush. I think this is a give and take situation, if one wishes to have extra safety, one has to accept extra disadvantage.
(e) Value for money
Despite Envy brush being graded lower by me in term of built quality and performance but due to its much cheaper price, its value for money in my opinion is higher than A7D if one has to take into consideration of every cent spent.
BTW Envy Brushes are more popular in its 5 sets package which has more value for money (RM48/set after conversion, excluding shipment & GST).

Nevertheless, in my opinion, only the largest size Envy Brush is most useful. I own the set but I wish now all 5 brushes are the largest brush size.
Attach also a picture showing side by side comparison of original Swissvax Brush (which sold at Ferrari price, so I do not own one) and the cheaper alternative Envy Brush.
This post has been edited by scoutfai: Sep 13 2014, 08:34 PM