One type shares the exp like it would when you give an Exp. share to one of your pokemon. The other type would share the exp like they were actually in battle, defeating the opponent.

For example:

Exp Share 1:  Lucario defeats Squirtle 1000 exp, Charmander with Experience share 1, will get like 500 or so
Exp Sahre 2:  Lucario defeats Squirtle 1000 exp, Charmander with Experience share 1, will get what Lucario got, which is 1000

Hope this helped =D