JVM is seriously more complex and heavier-weight. It does too much, and is shaped by Java the language too much (no functions, only objects!). It brings in mandatory GC. It's built around shared mutable data.
WA is much smaller, assumes way less, is isolated from DOM and JS code way better, communicates with them via message-passing. It has a smaller attack surface, and less room to screw up in the implementation.
Yes, I think not having WA married to DOM is a good idea from many angles. One of them is security, of course. Another is wider applicability: a WA VM could be useful outside the browser, and it already is.
WA is much smaller, assumes way less, is isolated from DOM and JS code way better, communicates with them via message-passing. It has a smaller attack surface, and less room to screw up in the implementation.
Yes, I think not having WA married to DOM is a good idea from many angles. One of them is security, of course. Another is wider applicability: a WA VM could be useful outside the browser, and it already is.