I've said it before and I'll say it again. There is no best pipe! There is a best pipe for a certain combination, but not a best pipe for everything.
There are many factors involved. Maybe I should say EVERY factor from the boat to the prop to every aspect of the engine and the fuel along with several other factors play a part in what pipe configuration will work best.
Another thing to think about is the power delivery. Do you want lots of punch off the corner or more top end? Yes, you can effect that difference with pipe length, but if you want the optimum then the pipe must be designed specifically for that purpose.
The OPS pipe is a good all around pipe. It works good on many applications, but it does have limitations.
The old Irwin S pipe was good for riggers and only so-so in monos.
Again, there are endless combinations and the only way to know what is the best pipe for your boat is to try as many pipes as possible.
And remember, don't just stick a pipe on an try it once....you may need to make a change or adjustments in other areas that will make a particular pipe stand out above the others you have tried.
Good boating!