How do you know the reduction is minimal, have you measured it? Though, I suppose if you've your pump at only half capacity, any losses are largely irrelevant. My situation is much different.
I don't personally like grinding holes through the back panel because in order to respect safe edge distances, it ends up being too low and back siphon is a problem. So, either you end up needing to raise the output with a bunch of ugly PVC inside the tank or use poorly-performing check valves. I suppose one could oversize the sump, but that gets problematic with larger tanks.
With a bit of attention to aesthetics, one can use over the rim PVC .... that is what I have done. I have a very large tank with a basement sump room, so squeezing as much flow as possible out of my pump is a priority. When you are dealing with 14' of calculated head pressure avoiding any and all friction losses is important. I cannot speak to the challenges of snails since I don't keep any (they just end up as lunch for my wrasses or hermit housing), but I just don't see the point of using velocity nozzles. I shoot my main return directly down behind the rocks and use in-tank circulators for the majority of my flow needs. But, YMMV.
I do use the VCA nozzles on my closed loop, but even there I am unconvinced that they really offer any net benefit (and they're uuuuugly).
