Both E99's come with a battery and charger to my knowledge. Don't worry about the "better" stock barrel because you'll eventually end up buying an aftermarket one. The Avant has 1 extra bps cap but you probably shouldn't worry about that because it takes practice to consistantly get that high even though just about everybody says they can. The Avant also has a plastic feedneck that might break. The classic E99 has a metal feedport that you can buy a metal feedneck for. It's up to you and your preference.
They are both the same except the new Imagine might run a little lower pressure stock which is not a big deal. Other than that your only paying more for the "newest marker" and if you like the looks better. For Spyders its not always "you get what you pay for" But its your $$$ do as you wish. But remember that you'll need extra $$ for a new barrel and motorized hopper.