Dalvik (Android's runtime) isn't really Java. It's an optimized subset of Java (they eliminated things that would slow it down).

I'm not sure you can really say which is better. Each one makes it choice based on larger issues than just executable code speed.

Android is designed to run on multiple hardware platforms (the multiple ARM variants, MIPS, x86, etc.). For that to work, while still providing a single user experience, native code just wasn't an option. And, this approach is probably a factor in why we're seeing Android pop-up on so many different devices (official, and unofficial). Why bother if you can't run any apps on it? or if you have to get vendors to port their apps to N different CPUs.

Maemo, on the other hand, only runs on a single specific hardware design. It doesn't need that support for multiple platforms. On the other hand, that also means it doesn't have the benefit of running on multiple platforms from multiple vendors. And, its approach would be awkward at best (for the consumer market) if it was deployed on those same platforms as Android.

So, one approach gets you CPU flexibility/independence and proliferation. The other approach gets you speed and maximum hardware utilization. Each one fits the higher goals of the people who made that platform. You can't really say which is better without addressing which of those higher level goals is better ... which, IMO, isn't an answerable question. It depends on what you/they want.