I think the main difference in V4 and V4+ is the plus has a more sensitive touch screen (easier to interact with) and also it's easier to see when there is glare on the screen.  Maybe processor upgrades?  But I don't think that was an issue on the V4 anyway.  V4 is about as easy to see/touch as a JD 2630.  V4+ is more like an iPad as far as screen sensitivity goes.  If $ savings is significant to you I wouldn't be worried about a V4.

I'm not sure if a Kinze has the normal Raven Viper4 software or something else on it?  That could be an issue.