I would say keep the E jets, since the LR versions have enough reach to get to the east coast of China and I think to Indonesia (don't quote me on that). It is incredibly expensive to terminate a lease early and could easily bankrupt you in the process.
As for A320 or 737 families, you first want to stick to a single fleet and engine type to keep maintenance costs low. Then it is up to personal preference although the A320 family offers similar range capabilities across the board compared to the 737.