The G4 Plus with 4GB of RAM(the base Plus version still has 2GB) seems a bit better about holding on to apps, but it’s a marginal difference in daily usage. The SD617 is the main performance bottleneck.
There are times I feel like I’m pushing the device right up to its limits when I’m jumping between apps or editing images. Still, it holds up fine and doesn’t feel sluggish unless you start playing games. The Moto G4 tends to get bogged down easily if you run a heavy 3D game—the Adreno 405 GPU just isn’t hearty enough for that.
These phones both have a 3, 000mAh battery, which by the way is 400mAh larger than the Moto Z. Battery life is a very personal thing. My usage patterns may be vastly different than yours, so consider that before you take any of this as gospel. With that out of the way, my experience with battery life on the Moto G4 has been fantastic good.