Another advantage to having the tenants pay through a bank is you have eliminated the chore of having to keep going to the PO to see if a payment has come in. When I used a PO in the past, every now and then I had to deal with a “the check is in the mail” situation. That is a hassle the bank idea eliminates from your life. Once I found a few checks in my box that post office had put in someone else’s box until they were discovered by a neighboring box’s honest owner. In that case a few of my tenants’ claims of “but I mailed the check on time” was correct. Again, the whole thing was a big hassle and there was some unnecessary hard feelings.
But if you feel you have to go the mail route, you can always have them mail the payment to the bank. You could type up some kind of deposit slip that you could provide to your tenants who complain about having to go to bank in person.
Once you get everyone trained, I see more advantages and fewer disadvantages to the bank method than any other.