This link from the EPA seems to indicate (in section 8.2.5) that UV is a reasonable disinfection technique for bacteria and even protozoa such as Cryptosporidium which chlorine barely touches (also Giardia cysts where UV is better than chlorine). However, UV is worse for inactivating viruses than chlorine. In any event, chlorine is still needed as a residual disinfectant in the main body of the pool water.

Technically, if you are going to have a separate stage disinfectant, ozone might be better, but only if chlorine is used as a residual. Though ozone will reactivate bromide to bromine, it can also form bromates. Ozone will also help break down organics so for indoor pools trying to keep CC low, this might be a decent option (compared to using non-chlorine shock, KMPS, weekly).

Richard