I believe it's been said that the plan for 2.0 is allow passive placement of spies who will gather intelligence without sabotaging anything, and won't be able to be nullified by the AI (for effectively the same result as the DL system), but don't quote me on that.
End of quote
~taps the quote button~
Sorry...had to.
Until I see something quotable for the 2.0 changes, I'll not spread on 'well kryo said this'.
I just wouldn't mind the hybrid of the two. Getting intel via un-destroyable spies and then some destroyable spies that sabotage. That way you aren't wasting funds like mad to just learn things, but when a spy shuts down a factory...he should have the ability to get shot at and nullified.
*edit*
That said, I think the tech stealing should be stoppable, thus the destroyable spies should be the ones w/ the chance to steal techs. Overall numeric knowledge of a foe is one thing, but once you steal/shut something down, you need some sort of defense against that IMHO.