I have never seen a measureable difference in group size on my rifles fitted with a Holland or similiar design compared to a radial ported break such as the Vias.
I have however observed some braked rifles to not shoot well as a result of poor fitting of the brake in alignment with the axis of the bore. Mainly from not reaming the bore accurately with the axis of the bore.
When you compare a partition style brake such as the Holland against a radial ported brake, both will have advantages and disadvantages.
With a muzzle brake, the faster the escaping gases are deverted, the more efficent the brake will be at reducing felt recoil.
Also, the faster the gas is released, the louder the brake will sound to the human ear.
So yes, the Holland will be a bit louder then the Vias type brakes but it will also be more efficent at reducing felt recoil.
One thing I personally like with the Holland brake and similiar designs is that you can ream the bore hole quite tight compared to a multi baffle radial ported brake. The reason again is because the gas volume is released so quickly that you can make the bore hole much tighter to the bullet diameter, which in effect creates an even more effective muzzle brake.
On a radial ported brake, you have to keep the bore hole a certain amount above bullet diameter because you are limited in the amount of gas that can be released in a given amount of time.
THis also depends greatly on the cartridge you are using and the barrel length on the rifle as these two factors greatly effect muzzle pressure is what makes a muzzle brake work. The higher the muzzle pressure the better it works.
So in my personal experience, I have never been able to tell an accuracy difference between the two types of brakes. Only that the partition style brakes are more efficent at reducing felt recoil.
THis is the most efficent brake I have yet to shoot. Not that it is much better then any other partition style brakes but on my 338 Kahn, it reduces recoil with a 300 gr ULD RBBT at 3100 fps to that of a 22-250 heavy varminter. The brake on the left is a 5/8" Holland QD brake.
This is the brake fitted to the Kahn. The reason it works so efficently is because the bore is reamed very tight to bore diameter and the contact area on the partitions is very large. The larger the area on the partitions the more efficent the brake will work. You will also notice there is no top ports either as there are with the Holland. In spite of this there is ZERO muzzle jump with this rifle but that is probably due to the stock design as well as the brake.
If the rifle is built properly and the brake fitted correctly, groups like this will be the result with either design in my experience.