I think it depends a lot on your set up. Most of us have false bottoms/drainage layers so it's not necessarily practical to stick an undergravel filter in there, and you may not have any gravel at all (in the case of a false bottom).
I think that with amphibians that are being misted regularly and often in a viv with a recirculating water feature, the act of flowing down the feature, into the pond, then into the false bottom provides a lot of biological filtration (it does depend on your bioload.) Also, if the tank is being misted often, a lot of the water is being replaced over the course of a week.
If supplemental filtration is needed, I always like the sump with a wet dry trickle filter for ease of set up and maintenance. It's really cheap (you can make them out of plastic containers of any size,) and you can service it without tearing apart your tank.
If it's not practical to have a second container below your viv for a sump, maybe an undergravel filter may be a good option. I'm avoiding any major water features for a while though. I'm tired of leaky plumbing, moving buckets of water, etc.
Cheers