It is certainly true that a Flywheel takes more time to charge, but they have some advantages. They do not suffer from the breakdown problem caps do. They also generally do not explode it grounded out. They can usually hold a charge longer than a cap and they can always be charging. Finally, and this is the reason that at my last gig we used them in certain places, they are excellent surge supressors. (again that whole explode thing) Honestly I would not be surprised to see both. Again, much would depend on the service they are planning or have at their disposal.
Also flywheels are just cool.
Also flywheels are just cool.