I've had Mecers fail, seen RCT fail etc - go for the cheapest one and get it over with. Even with no load, the battery % will fall, but should stabilize at some arb 60% level. Sure, it won't run for 9000+ hours, but should last at least 2+ hours. My Mecer el-cheapo UPS runs the TV for 2 hours without a problem with my set of batteries, so should also run the same time with no load.
Do note though,I have heard that some lower VA UPSs have a 2 hour hard limit on the runtime - my Mecer 650VA does this, even with no load. Mildly irritating, but not the end of the world.