Android Studio's minimum-resource-usage-for-sane-performance is enormous. It does some things nicer than Eclipse, but there are definitely times I miss Eclipse's lean-ness, which is not a thing I would have expected myself to ever feel prior to AS.
It's big and slow, agreed, but it is very powerful. I don't know the details of the virtual FS layer but I can sympathise because that's very difficult to get right in a cross-platform way.
I don't think it's powerful. As fanatic as it seems, emacs is more powerful for real work. It's more human and more theoretical than Eclipse, which is a "usine a gaz" more than anything. It doesn't bring performance, nor ease of use, or stability. I don't get it.
The graphical views are useful, and the wide range of plugins comes in very handy. I could never get on with the emacs interface - it just wasn't discoverable enough - YMMV I guess.
Discoverability in emacs is a tiny bootstrap problem. I have to admit that for years I didn't know how to ask emacs, but when you do (C-h m, C-h k), there's no more discoverability problem.
And actually it does use less resources than either InteliJ or Android Studio, while having faster builds.