OSPF External Type 1 and Type 2 Comparison

E1 Routes: Both the external cost and internal OSPF cost matters.
E2 Routes: Only the external cost matters (unless there is a tie).

Use E2 if the goal is to always send traffic through one ASBR.
Use E1 if the goal is to balance the traffic, and make each router pick the closes ASBR.

CCNP-TSHOOT 642-902 Official Certification Guide