Your statement that Shimano DI2 can only be shifted one gear at a time is wrong. Not only can it be set to shift continuously for as long as you hold the button down, you can set the time interval between each shift (faster or slower).
Also, I beg to differ on Sram's battery charging being easier. Initially you'll have two batteries to charge and two to install in the shifters, vs one battery to charge and zero to install for Shimano. After that, you will be recharging at least one Sram battery every 60 hours (approx 1000 miles), while my DI2 battery is good for around 2500 miles. It doesn't take a rocket scientist to see which is less labor intensive.
Those aside, my biggest complaint about Sram's system is that you can't shift front and rear simultaneously. When approaching a sudden elevation change, up or down, I like to dump the rear derailleur two or three cogs while shifting to the appropriate chainring at the same time. That isn't possible with Sram electronic shifting. I've yet to read a review that points this out, but it's always mentioned in the comments section so I I'm know I'm not the only cyclist who considers this a design flaw
Long story short, the only advantage Sram has over Shimano is that their system is wireless, which doesn't outweigh the disadvantages, in my opinion.