Dalvik is a highly customized Virtual machine for Android. If you have ever visited the Android FAQs page, you will find links to a few resources which detail Android's DVM.
In general, Dalvik is register based virtual machine and the regular Virtual machines from Sun(both for desktop and KVM) is Stack based. AFAIK, these are two separate architectures for designing a VM and the question as to whether which of them is better is akin to the "RISC versus CISC" debate. There are numerous articles on the internet ; google "Virtual machine Showdown"