Regarding the similarity between the guns they are superficially similar in some ways but very different in construction.
The hw100 is modular and much easier to work on, with pretty much all steel construction, so very very robust.
The hw110 is a single outer plastic/polymer shell with numerous small metal components inside. The quality of construction interally is fine but not anything like the hw100.
The triggers are similar in feel but not design. I think the hw100 trigger is better overall. The hw100 trigger group is also entirely removable and can be set up entirely to preference while off of the gun, which makes things much easier and potentially safer.
The side lever on the hw100 is smoother, at least on my examples and the magazines on the Hw100 are higher capacity, much smoother to insert and lack the sandpapery rough anodizing of the hw110 mags.
The cylinder on the hw100 is removable, so fixing a leak down the road is easier and degassing is a non issue. You can also buy spares for the field if that's your thing.
Power output is no different, so just about the only advantages the 110 has to my knowledge are weight and a relatively small decrease in price