I really enjoy both species.
P. terribilis:
- Very bold
- Large & impressive
- Loud, pleasant call
- Can be kept in groups
Tend to be intolerant of overly wet conditions and higher temperatures. Require more space.
D. leucomelas:
- Tend to be bold
- Pleasant trilling call
- Sharp, variable patterns
- Can be kept in groups
- Hardy and tend to be slightly more forgiving of small beginner mistakes that may happen.
Leucomelas are probably the best 'beginner' frog but if you do your research and remain diligent, terribilis are also a good choice. Note that I said "small" mistakes -- meaning that little things can go wrong or need tweaking if you're inexperienced, but so long as you do very thorough research from good sources, like this board's deep archive -- bigger errors shouldn't happen.
If possible, I would get a taller tank. Mine (both species) will use all the space given to them. Especially the leucs, but my terribilis also climb frequently. You'll also lose a lot of height to things like substrate and false bottom construction.