[Bob Putnam]

If you use a dual (tandem) cylinder, there's no difference in safety between the balance bar system. The advantage to the proportioning valve is that you'll get slightly better front brake pad longevity. The disadvantage is more effort may be required on hard stops. For efficiency reasons, a dual-bore master is almost manditory too.

Both systems are dynamically adjustable, although that is "optional" with the balance bar design, and may require line re-routing with the prop valve.