Issue #1... Possible weight increase.
Issue #2... Will have you spending hours researching tire.
Issue #3... Bigger tires can be more expensive.
Issue #4... More traction
Issue #5... More traction will have you adding HP.
Issue #6... Possibly too much male attention.
Issue #7... You may stop doing other things you use to like, so you can touch your new larger tires all the time...
You have been warned.
Note: Mine are 19x11 up front and 19x12 out back.