I have two of them! They work well as I sleep so, finishing at 2AM or 6AM doesn't matter to me. I have a Nitecore for fast "oops" charging needs.
What charging speed does the nitecore have
The Nitecore D4 will charge 1 to 2 batteries at 750ma and 3 to 4 batteries at 375ma.
Vapcell S4 Plus 3A , this looks like a slightly better charger, feature wise, than my miboxer c4-12…? correct?
Is an 8 cell charger better than two 4 cell chargers ?
I have broken out two chargers at the same time before, but rarely. For me it seems to make more sense to have a pair of 4 cell chargers vs. one bigger one.
I prefer 2 4’s… the 4’s can be had in 2 or even 3 amp charging rates - for all 4 slots.
In the beginning of this addiction it seems like overkill , but really think ahead. Soon you’ll have like 15 lights and 30-40 batteries
What are you saying ?
Is someone planning on breaking into my house ?
I have a pair of 8-bay Xtar chargers for overnight slow charging batteries. I also have a handful of 4-bay chargers I could use as well but, plugging in two 8-bay chargers wins most of the time.
In terms of faster charging one or two batteries, 1 battery in an 8-bay charger just isn't practical. My 4-bay chargers will 'fast' charge two batteries at a time so, it is any easy win for 4 or 6 batteries if I need to top them off late in the afternoon for the evening flashlight fun.
Vapcell 8-bay charger with capacity test feature sounds interesting… But if all slots are doing discharging/capacity test, that will produce a lot of heat, maybe a cooling fan would then be needed…
Also, 8-bay if charging at 2 Amps per bay, will require more power than 4 bays at 3 Amps per bay… Will likely need a more beefy power adapter.
The S4 is a big charger, how big will the 8 bay be?
“Currently”, I use 5, 4 bays and two 16 bays; takes 1 backpack to hold them all; just trying to minimize.
Still just “meditating” on the suggestions.
Pic of this conglomeration later. 
The megacell charger is 16 bay.
You need a phone or pc to controll it though.