David you did have to open pandoras box.......
It had been a while since I looked at chargers and had been recommending the I4 for those that have asked and have been using them for 5 years or more. I searched and found enough stuff to keep my head spinning for a while. I first found this in a thread from 2015 on another site. It compares the I4 VP2 and the Opus which I never heard of. Also the Xtar VP2 will only charges LI-ON and won't charge NIMH.
If you want any and all of your li-ions charged right, go with the VP2
If you want your batteries to be analyzed, combined with a decent charger for both li-ion and nimh, go with the C3100
If you want a charger that just works, or are on a budget, and want to charge both li-ion and nimh, go with the nitecore I4 or I2
http://www.ebay.com/itm/Opus-BT-C3100-V2...S-/232339823449
Like 1trkyhntr said lots of info on the vaping sites, I think that's the driving factor in chargers today, there is so many more choices. Here's links to Nitecore and Xtar
http://www.xtar.cc/products_list/pmcId=24.html
http://charger.nitecore.com/
This is the older version I4 I've been using, no buttons for choices just load batteries, indicator lights just show charging status.
http://www.ebay.com/itm/Nitecore-i4-4-Sl...2267568065?hash
I'm not sure what I'd get today, but I'd want it to charge both LI-ION and NIMH batteries with a 4 battery capacity.