Multi-family pay laundry

[Dan KIllinger]

I am adding pay laundry to a new multi family property I have acquired.  I have research the following payment methods.  Does anybody have any insight into which of these has worked the best for you?  Or might you have any other suggestions or vendors/readers you recommend.  I own 3 commercial Maytag units that are ready for readers to be installed.

1. QR code

2. Credit card

3. Laundry card you put money onto 

Thank!