MBB will offer better exit opportunities.
The reason is, some companies hire just ex-MBB (this is particularly true in highly-competitive industries such as PE).
Whether it is "significantly" better, depends on the exit you are targeting (if it is PE for example, I would say the difference will be significant).
It is totally fine to join a 2nd Tier though. You will have good exits anyway and you can always move to MBB later on if you want to join.