The conventional wisdom has been to avoid an EMH park if you were not going to take full advantage of the extra hours - e.g., if you are staying off-site and can’t do EMH, you should not go to an EMH park. The reason behind this is that the park would be more crowded during normal hours because of all the extra prople who went there for EMH.
However, I recently compared TPs for MK on days with the same CL but one day had mEMH and the other did not. I made optimized TPs with the same attractions for each day, but just using the normal park hours. The non-EMH day had a longer overall wait time, but the difference was not very much, and definitely not great enough to warrant saying that the day should be avoided.
At the end of the day, you should choose the days that work best for your personal schedule. Take CLs, EMH, ADRs, and overall park hours into consideration when choosing days, but the most important thing is to make a good TP for each day. If your TP has you doing all the things that you want to do in a reasonable fashion, then you are set!