Re: real performance difference between 178 and 208 amax
The answer to your question can be easily answered with a ballistics program. Just plug in all the relevant data - bullet weight, BC, velocity, cross wind speed. Then run the numbers for both. Watch for differences in trajectory, energy and wind deflection.
Liltank is probably right that you will probably see little difference between the loads until you get past 800.
I'm not gonna shoot here. I'm gonna shoot waaaaaaaay over there!