I recently switched from horizontal, bottom located spray bar to vertically oriented. My "original", horizontal spray bar was much longer and all the holes were 1/8". It seemed to create a nice gentle flow. I couldn't see any dead spots in the tank (noted by accumulation of debris), but I also couldn't really tell you what the circulation pattern was. Depending on the upward angle I set the spray bar, I could get or remove surface scum.
When I switched to vertical (*and* removed the DIY external reactor), I set it up in the back left corner of my tank, right next to the intake, pointing into the back glass. The flow was much more definite...clock-wise around the tank! But, I could also detect a faint whistling from the filter. The next day, it hit me that the reduced number of spraybar holes might need enlarging. As it is *much* easier to increase the size, I went up once 'notch' first...I think they're measured in 1/64" increments. There was still a humming. So, I went up a second notch, and things quited down. I've only been using it for about a month, and as I have the spray bar pointed somewhat downward, I'm still getting a small amount of surface scum. But, I think I'm gonna like it.
Two benefits (in my mind) that I noted right off. First, it was cool to see many of tetras and rasboras "playing" in the new vertical stream. They seemed to enjoy swimming against the new flow. Second, many of my cories and bottom-dwellers saught out the "least" movement in the tank. Previously, this was under my horizontal spraybar along the back of the tank. Guess where it is now?!? Right in the middle of the tank! So, I get to see many of my cories much more easily than before.