Dalvik, and Dalvik's JIT compiler are definitely tuned for small batteries.
The Dalvik JIT compiler focuses on critical sections of code. There's a reason you don't see Hotspot on battery powered devices.
Large amounts of the Android framework, especially the foundations of drawing and the View hierarchy, are in C or C++. Compiling an interactive app to native code makes much less difference in performance than a synthetic benchmark of DEX interpretation might lead one to think.
Hotspot get its name from the term of art for a critical section of code, though. That's not something that makes them different from each other; it's what they have in common.
What separates them must be that only one of them was designed with a power budget in mind.