If you can effectively run one core, each run will often be taking just a little longer than a two core setup, while rewarding 50%-80% more medals with the extra stages you can now run. However, as you progress through the game, sooner or later you should realize that spending medals to enhance two units is actually a liability, since you only need one strong unit to effectively kill everything except immunity bosses. This way you can easily kill both physical and magical immune bosses enabling fastest run clear. If you are just starting to play this game, it is recommended to Two Core setup your units, which means evenly distribute your medals to one physical damage dealer and one magical damage dealer.
