Here are some screen shots I took on my two test devices. This is with the games running as apps built in XDK (not testing locally in a browser).
Nexus 5X: 60fps, roughly 50% CPU usage (Is that good? I dont know how good that is).
This is smooth game-play, snappy menus etc. V happy with this performance.
iPhone5: fluctuates between 40-50fps, CPU usage fluctuates between 80 - 90+% (looks pretty high right?).
Another problem with the iPhone not reflected by these numbers is that each level in the game takes a long time to load. 4-5 seconds compared to about 0.5 - 1 second on the Nexus. The game-play is 'playable' but not great. But I really want to fix the lag with levels loading. Thats a problem.
I did an additional test. I had a suspicion that it could be the way I was using tilemaps in my game. Each level has 5 layers dedicated to tilemaps. I built the levels that way because I wanted to layer the background to have a foreground, midground and background. And I have two layers for collision tilemaps, one being solids and one having the jumpThru behaviour.
So I wondered if all these tilemeaps might be causing slow performance on the iPhone, so I deleted out the layers with artwork in them (highlighted red in the image below) and just left the two collision layers (which are invisible in the screen shot).
This seemed to have a small effect on FPS (45 - 55fps) and CPU utilization (80 - 88%). But it improved the load times of each level a lot! The levels now load in about 1 second without those additional tilemaps.
So if I want my game to run nicely on lower end iPhones, Im going to have to improve the way I make my backgrounds and use tilemaps differently. Otherwise it will only be people with decent phones that can run my game
... Id like to test on an iPhone6... and Id also like to know how many people use iPhone5 and below globally...