I don't know, my experience is that it is very hard to tell if the model is better or worse with an update.

One day I will have an amazing session and the next it seems like it has been nerfed only to give better results than ever the next day. Wash, rinse , repeat and randomize that ordering.

So far, I would have not be able to tell the difference between 4 and 4o.

If this is the new 3.5 though then 5 will be worth the wait to say the least.