The iPad Air 2 has a huge CPU and GPU performance over the iPhone 6, but until last year both the iPad Air and iPhone 5s shared the same A7 chip.
My question is, the iPhone 5s had a much smaller resolution than the iPad Air, and modt games on the App Store says "optimized for iPhone 5". Does that mean that until the new A8X the iPhone Air would run all games at 30% or less performance than the iPhone?
Let me give you an exemple: The Wolf Among Us didn't run so smooth on my old iPad 4, but was it going to run 30% or more better on an iPhone 5?
I'm just curious because until the Air 2 both iPhone and iPad would share the same processor, but with the iPad having a much higher resolution.
"Optimized for iPhone 5" just means that the app has been updated to fill the full 16:9 aspect ratio of the iPhone 5. Back when the iPhone 5 came out, many apps had bars at the top and bottom of the screen because they weren't updated for the new screen size. "Optimized for iPhone 5" just means it will fill the screen size. Nothing to do with performance. However a performance edge may exist whether the app was "optimized for iPhone 5" or not, it's just because in every situation the iPhone 5 has less to handle, even though the iPad 4 has a slightly more beefy chip.
iPhone 5S does have a bit of an edge over the iPad Air, mini 2, and mini 3 because they share the same chipset, yet the iPhone doesn't need to handle as much in terms of screen resolution.
Gonna give a little lesson here, it is going to be a bit long so bear with me.
One thing to consider is when comparing the A7 to the A6X, they have the same amount of GPU cores. An A5X/A6X chip means that it has added GPU cores compared to the regular A5 or A6 to help graphical performance due to the high resolution screen. The regular A5 chip has 2 GPU cores. The A5X has 4 GPU cores, the A6 chip has 3 GPU cores while the A6X has 4. The regular A7 chip has 4 GPU cores so making an A7X was unnecessary. Plus improved architecture and 64 bit improved performance over the A6X. Despite all that though, the iPad Air, iPad mini 2, and iPad mini 3 struggle a bit with the graphically demanding translucency in the UI of iOS 8. On top of that, the A7 only has 1GB of RAM. 1GB of RAM on a 64 bit chipset along with a 2048x1536 screen is bad news. I think Apple learned from this and returned to the "X" series chips for iPads. The regular A8 chip has 4 GPU cores, 2 CPU cores, 1GB of RAM and 2 billion transistors, it's clocked at 1.4GHz. A8X has 8 GPU cores, 3 CPU cores, 2GB of RAM, 3 billion transistors, and it's clocked at 1.5GHz I believe. So the iPad Air 2 has a huge edge over the iPhone 6 in terms of GPU cores, CPU cores, clock speed, architecture, and amount of RAM. It sort of is needed though since it has a much higher resolution screen.
Unless the iPad has a complete overkill processor like the iPad Air 2, it will always be slightly less in performance compared to its iPhone counterpart. It is just how it is because of the screen resolution.