@MajorC I would just go with the 4GB version as it is not a massive difference in price. Now that the Pi has better graphics we are likely going to see much more capable and sophisticated modules. I’m thinking in particular things like facial recognition can get to the point where it is much more responsive than it is today (not sure if the extra memory helps in this particular scenario, but it’s just one example of many I’m sure).
Given how long it took for the 4 to be released, you’re better off future proofing yourself as much as you can now. It would be a shame to be handcuffed by a relatively inexpensive option you decided not to get.
If you haven’t built a mirror yet, you’ll find that the price of the Pi is one of the least expensive parts of the project. Go with the best available.