In my experience, the newer stuff with the sealed carbs will run exactly right with the manufactures recommended 40:1 mix. When you try to run 50:1, the engine runs terrible, as the fuel ratio is now off and the engine carb needs adjusted. I have seen this several times.
If you mix it yourself, try 45:1 in both as a compromise. If you buy the premix cans, try 50:1 and see if it works. If it does, great. If not, then you might need to keep two types of fuel around.