Do you swap batteries in your G3 today? If you do, I will bet that "bigger battery" thing with the S7 is not going to be as sufficient as you think. My S6E chews through its battery untethered in under a waking day. I expect the S7/S7E to do the same thing at a higher rate, even if the battery is slightly larger than the S6.
I want to stay with the Galaxy. I really do. I'm used to the design, and I've been a Sammy customer for four Android phones (and a Palm OS one, BITD). But, I've really, really missed the swappable batteries from my S5 over the last year with my otherwise-quite-nice S6E. Now, in order to last more than just breakfast to happy hour, I have to have my phone in a Mophie case, which makes it huge, or carry a battery pack and cable combo, which makes the phone a lot less "wireless" than one hopes a wireless phone will be. Plus, those external battery packs, when large enough to provide anything beyond a brief emergency reprieve on battery drainage are as large as the phone itself, volumetrically. Or, I have to have a cable and a charger (the very specific QuickCharge2.0 charger, if I want it to be anything less than sluggish taking its juice) and orbit wall sockets all day, also raising the wireful factor of this wireless phone, and increasing the bumps in my pockets to boot.
I know that to some, carrying extra batteries is the same as carrying a battery pack, but a PAIR of fully charged batteries isn't even the size of one of those external packs. And, their thinness makes them perfect for sliding into pants pockets unobtrusively. (Unless, of course, you're a skinny-jeans wearing hipster, in which case you have larger life choices to question than which cellphone you're going to buy.) And, the "recharge" from a swapped battery is instantaneous, as opposed to staying tethered to your Li-ion anchor for three hours while your slab gets its juice.