Here is some info to help with your decision.
If you want to bring a LiIon battery to storage voltage using the Opus, you can do this. First do a straight discharge. I do it at 500mA, when it finishes the batteries are at about 3.1V, then I do a charge with the voltage switch set for 3.7V or the LiFePO4 setting. When the charger finishes your batteries are at 3.7V, just right for storage. You would not be able to do this on both the Liitokala Lil 500 Engineer and the Xtar Dragon because both don't support LiFePO4 cell charging.
The MC3000 is in it's own league. It has a true storage mode where it will charge or discharge at whatever current you set in order to reach whatever target voltage you set.