Tried several OVPN, furthermore, with a good quality network coverage plus a correct settings can give a good quality internet connection. On the other hand, injectors can be much of a headstart sometimes depending on the given EHI file.
When it comes to FREE internet service, there'll be ups and downs to be considered, always.
Bottomline is, whether it's an OVPN or HTTP Injector(s) as long as its FREE for use. So yeah, looks like it's a 50-50 for me based on my experience.