Don't overlook the bandwidth overhead of html fragments vs. json snippets. That issue is magnified on mobile.
Additionally, if you are doing small updates the DOM API is faster than injecting .innerHTML. I think this has changed in recent years and .innerHTML might have caught up for larger nodes. I personally still use the DOM API because it encourages more simplistic layouts.
Also remember that it's usually latency and connections that kills mobile performance. I've also found the actual data transfer to be fairly good compared to your average domestic DSL.
Additionally, if you are doing small updates the DOM API is faster than injecting .innerHTML. I think this has changed in recent years and .innerHTML might have caught up for larger nodes. I personally still use the DOM API because it encourages more simplistic layouts.