Dear robert,
I think our numbers reflect a combination of surgeons prefrences and patient's choice. There are pros and cons to mechanical and tissue valves so ultimately it is very much a personal choice. Given your frequent nose bleeds this may be a reason to prefer a tissue valve. On the other hand you are young enough that a tissue valve may need to be replaced whereas a mechanical valve probably would not.
If you would like to be seen here at the Cleveland Clinic I would recommend Dr. Lytle. This would give you a full range of options for valves. You can make an appointment to be seen here by calling 1-800-CCF-CARE and asking for an appointment with one of the F15 "valve" cardiologists.