@Access everywhere
Please pick freely according to your preferences. Hummingbird is much faster, has a tiny RAM footprint (less than 10 MB), it's based on OpenVPN3-AirVPN library, and does not require Mono, but it lacks a GUI (it will evolve with a daemon and GUI only in the near future) and many features of OpenVPN 2 and Eddie.
Eddie is remarkably features richer (full integration with AirVPN infrastructure, customized routes, customized events, OpenVPN over Tor are just a few of several significant features that Hummingbird totally misses), offers a complete GUI, but it is much slower and has a huge RAM footprint (exceeding 1 GB in Linux for example). Please note that you can run Hummingbird through Eddie (Eddie 2.18.7 or higher version required) simply by ticking "Use Hummingbird if available" in "Preferences" > "Advanced" window and copying the Hummingbird binary anywhere in your commands path. In this way Eddie will run Hummingbird instead of OpenVPN 2 and you will have the hardened security of Hummingbird vs. OpenVPN 2, as well as a significant performance boost in various phases (during connection and disconnection Hummingbird is up to 300 times faster than OpenVPN 2).
Kind regards