The GV Mobile + in Cydia is no longer supported. It went into the legit app store a while ago. Which one is better is up to you, I prefer the UI of GV Mobile + so I'd say to grab that but make sure you get it from the Apple App Store.
What is your opinion on GV Mobile? I have tried both apps from Cydia and the App Store and really am not too happy with either. The version from Cydia didnt seem to support push (I could be wrong) and I had login issues with the App Store version for some reason. Ultimately, I went back to using Google's own Voice app which I really wish I didnt have to. It lags reallllllly bad sometimes upon opening/switching to the app. This happen to you...??