I've got Pods under just about everything now. Before that was all springs. Before that was all BDR. Before that was a lot of different things. Each transition involved trying the different things under different components. All kinds of combinations too. Like one time had 2 BDR Cones, one Nobsound. Another time two Pods one Nobsound. Three and four. You name it I tried it. Massive actual hands on experience.
Bottom line, don't sweat it. Vast majority of improvement is simply going to Pods. Pods are so much better, one time we had a DAC, this thing was so small and light I had nothing that 3 would work. So we fussed around until we got it balanced on just one Pod. Rickety as all get out and even had to put a weight on top because it was still too light but even so the improvement was there.
Tried stuff like this a bunch of times. Mostly out of necessity. Once you get used to how much better these are you just want more. So what if I take one from here, move it over there, put something else in here?
That is why I say don't sweat it. Instead, focus on each component because they are all different. A tube integrated might have 80% of the weight across the back while the front has almost none. You could order 2 for the back end weight and 1 for the front end weight if you are really trying to save that extra little bit. But in the long run you will probably find yourself better off with 4 all the same, because they will be easier to mix and match when you change components over time. Hard to know these things in advance but that is why I say don't sweat it, there are other factors besides sound quality to consider. If the difference in SQ was big that would be one thing but in this case it just isn't that big a deal.
Another factor is practicality. Some component you never touch or move or connect stuff too you might be fine with 3. But each time you do it will be a little less stable and prone to tipping. So all these little things factor in and again, are more a concern than 3 vs 4.
Finally, if you are down to splitting hairs let's really split hairs. The difference between 3 and 4 is less to do with 3 vs 4 than which combination is more perfectly matched to your component mass. Because Pods are made to different weight ranges, but not ounce by ounce they could never stock em all and it would only drive everyone crazy. So they are in a range with some overlap. Very clever, very convenient. It does mean however there could be times when 4 of one size is slightly better than 3 of another size. Or vice versa.
So there is a difference, 4 is generally better, but not by much. I would get whichever you think will look or work better from a practical point of view- and when in doubt go with John's advice, he has been doing this a very long time and never steered me wrong yet.