I am not shooting UGF down becasue of my unfamiliarity with it. I grew up with UGF and used it as my first and excluisive filtration for many years in my childhood. It was initially designed to run on air lift. Contempory outside filtration at that time was a lot more expensive and didn't work that well. My first outside filter was a Superking HOB that run on 45 watt electiricty and sounded like flushing the toilet. Worst of all, the siphon tubes needed to be restarted from time to time. The early magnetic drive HOB were highly unreliable because the magnetic couple slip easily and could overflow and wet the floor.
Modern outside filters are far different. In comparison with modern outside filters, UGF isn't the cheapest or easiest to maintain. I can replace the media in an HOB in minutes without even unplugging the unit. Cleaning an UGF isn't easy. One needs to vacuum 2 inch of substrate above the UGF plate and beneath it, which is much more time consuming than vacuuming a 1/2 inch substrate in a bare bottom. In term of maintenance, I would place HOB, sponge filter, wet-and-dry, canister and UGF in the order of increasing complexity. In term of performance, there is no difference and all will perform well provided one cleans them regularly.
Modern outside filters are far different. In comparison with modern outside filters, UGF isn't the cheapest or easiest to maintain. I can replace the media in an HOB in minutes without even unplugging the unit. Cleaning an UGF isn't easy. One needs to vacuum 2 inch of substrate above the UGF plate and beneath it, which is much more time consuming than vacuuming a 1/2 inch substrate in a bare bottom. In term of maintenance, I would place HOB, sponge filter, wet-and-dry, canister and UGF in the order of increasing complexity. In term of performance, there is no difference and all will perform well provided one cleans them regularly.