I had the TIR 4 and now I have the 5. I have used both software on both models, and the software is just a different layout, it really has no functional difference with the basic TIR usage.
As for whether the resolution difference changes things, all I can say is it makes a big difference in actual usage. Disagree if you will, but I have tested both. I would imagine people are going to try to convince themselves that it's not a big upgrade because they don't want to spend the money. That's fine, but in real usage I can tell you the TIR 5 is MUCH better.