Also, for your points (according to you),
you can create the exact same "challenging" feel of the low server in the high server, by playing past lv 221 on the high server. You said that you would not feel like grinding if you reach lv 221 because you did not need to, just like you said you would not feel like playing something over and over in the low server, thus causing the exact same mental difficulty on the fact that you do not want to play even more on the high server. Plus you should also add in the challenging side of guild in high server, for the "grind to rank 1."
Thus for your logic the mental and physical difficulty for low is = high, as you can create an = amount of feeling towards them being challenging.