Screen
The phones' screens nearly the same size --- a 5.7-incher on the S6 Edge+ versus 5.5 inches for the iPhone 6 Plus. But the Edge+ has superior resolution, 2560 x 1440 versus 1920 x 1080 for the iPhone 6 Plus. The S6 Edge+ also has 518 ppi versus 401 ppi for the iPhone 6 Plus. Winner: The S6 Edge+.
Processor and RAM
The S6 Edge+ has an Octa-core Exynos 7420 processor versus the iPhone 6 Plus's Apple A8 with motion coprocessor. That's likely a tie. But the S6 Edge+ comes with 4 GB of RAM versus the iPhone 6 Plus's 1 GB. So we'll give the edge to the S6 Edge+.
Size and weight
The S6 Edge+ is a little bit thinner and a little bit lighter: 6.9 millimeters versus 7.1 millimeters, and 153 grams versus 172 grams. But those differences are too small to make much of a real-world difference. A large phone is a large phone, despite a few grams here and there.
Camera
The S6 Edge+ wins this one, with a 5 MP front camera and 16 MP rear camera, versus a 1.2 MP front camera and 8 MP rear camera for the iPhone 6 Plus.
Storage
The iPhone 6 Plus gives you more options and can have more total capacity: 16 GB, 64 GB or 128 GB versus 32 GB or 64 GB on the S6 Edge+.
Operating system
This is the big one. Do you prefer the simplicity and smooth elegance of iOS, or the more feature-rich but more difficult Android No winner here; it's like arguing religion.
The bottom line
When it comes to specs, the S6 Edge+ is the winner. But the wild card is the operating system. The S6 Edge+'s better hardware isn't enough to make iOS fans switch. But Android fans will certainly want it.