ok when it comes to it exploration isn't all that bad, just depends on how many ships you send but yeah most was anwsered
as said pros
Dark mater
Res
Ships (never found any all that worth the wait)
Cons
aliens (+5 vs your Tech so say you have weapons at 5, they will have weapons at 10)
pirates (-3 vs your tech so you have a tech of 5 they have a tech of 2)
and nothing can happen you find nothing
its best when doing this to send one esp prob with them and they will report on what they might find so can give you advanced warning if you intercept pirate/alien transmissions, and you can recall, just let them duke it out)
and researching exp tech means you can have them stay out longer and increase the chances you finding something.