The difference is coverage, not features. The two versions use different mobile networks, so which one is useful depends on where you are.
4G is the newer network and carries mobile data much faster, but Ringo’s hardware and software cannot make real use of that speed. Day to day, the two versions behave much the same.
The 4G version exists because 2G has been switched off in some countries, the United States among them. Where 2G is still running, both versions work in much the same way, and in parts of Europe 2G is expected to outlive 3G.
There was no choice of version at checkout. The version supplied was matched to the region the kit was sold into.
Networks keep changing and switch-offs are still happening, so a version that worked when Ringo was current may no longer have a network to join where you live. Your mobile operator can confirm which networks it still runs in your area.
If your Ringo is not registering on a network at all, see “My Ringo can't connect to the network”. If you are not sure which version you have, message us here, or email [email protected], with your order number and we will check for you.