Vicky is way better for that period. I sometimes have the feel it would be better for WWII too. But for the combat engine, which is rather simplistic in Vicky, and I know many people plays HoI as a purely strategic wargame and not as a country simulator.
I really disagree about Vicky being able to simulate post 1900s period in any good sort of fashion. The mechanics in play are superior for country simulation, but the problem here - they are generic, sandbox and made with 1836 scenario in mind. It doesn't really feel like a whole century have passed, tech has changed and such, there is no character to anything.
For me the game really starts to drag after the 1880s.
I was always interested how did pride of nations treated the late 1800s-early 1900s period, but the damn game is near impossible to run on my PC.