64bit by itself is of limited benefit for a while in these devices (limited need in memory addressing or arithmetic). However, the ARM 64 bit instruction set is about as compact as it's 32bit predecessor, and includes a lot of optimisations (more registers, better SIMD). I recall that it also includes stuff that might assist with faster JIT for Android too. So even if you're not needing the 64 bit data size, there's lots of performance to be gained (but not because of 64 bit). In fact, it's a completely new instruction set implementation, not an extension of the 32 bit arm instruction set.