My favorite charger right now is the Nitecore UMS4. It uses the USB QuickCharge 2.0 standard so I don't have to worry about finding a suitable replacement for the external 12V DC power supply (and cord) that can break and that other brands typically use. My Anker USB QuickCharge 3.0 wall adapter piece, which is rated to 18W 3A, also saves more space on my table when compared to such an external power supply, and, having a total of 3A across the 4 bays is enough, as the UMS4 lets me adjust the charging rate on each bay in 100mA steps so I don't have to worry about the charging rate either being too fast or being too slow to get an optimum tradeoff between faster charging and reduced cycle life of my batteries. In addition, the UMS4 does not noticeably heat itself up underneath my batteries, which is a real bonus. Also I think the internal circuitry of the Anker piece adds on an extra level of safety protection. The Anker brand is well known for its high reliability when compared to external power supplies, the latter usually being cheaply made and requiring to be put on a non flammable surface.
As for how easy it is to insert and remove 20700 and 21700 batteries. The USM4 has significantly longer bays than really is necessary to accomodate this so the struggling to insert and remove batteries is now officially a thing of the past, and, the sliders are moving completely smooth and they are sturdy enough. The UMS4 is comfortable to use, has a clear easy to read screen that displays all relevant information, and the menu system is straightforward enough for it to be set up easy and fast. I also own a SkyRC MC3000, and that I rarely use. The only real reason why I bought the MC3000 was because it allows me to set the voltage cut-off to whatever the volts that I want. I vape on mech mods with complex coil builds, I am a coil builder so, sometimes, it can happen that I require the volts to be lower than 4.2V for how I want to vape.