I haven't tried them all but I guess it's the same sort of differences you would get from any range of mouthpieces with different tip openings. I have a 7 and it's my favourite mouthpiece. With a bit of luck Pete will be along soon and explain all. Generally speaking a wider tip opening will give you more volume but will be harder to control - which may well be an issue if you're new to soprano.
Also the facing numbers aren`t consistent across Makers ...
I prefer a wider tip opening of 7 (though it`a a Yani metal 7 which may not be the same as Petes) despite being new to the Sop as it gives easier control over intonation and the reed doesn`t choke up on the high notes ..
I tried four, 6, 2 different sevens and an 8. Virtually no difference in sound. I kept a 7 (with an experimental facing) and the 8. But as said above as the tip gets wider, potentially louder and harder to control. However as long as you match the reed to the facing, they're all easy to play. I mostly play the 7. Listen to Pete's samples for sound, but it's very much down to the player.
When I'm playing much, several hours every day, I play a mpc with wider opening and harder reed. Right now I'm on # 8 with #4 reed beacuse of lots of other things to do. Use to play #10 mpc with # 5 reed.
not me. But someone listed the sizes earlier. I found that the old rule of one opening size difference equated to half a reed strength change on them, so no need to worry that much. Even the wider tips are easy to play. A 6 would be a very good starting point if you're unsure.
It would not make any sense: tip size is a very personal thing. I am fairly sure I would sound much better on the 7 or the 8, and quite bland on the 5 or a 6. I think I heard Pete on a 6, and he was great.
Optimal tip size is related, among the other things, to:
reeds you use
ability of using diaphragmatic breathing
your favourite players
experience as a musician
I have another soprano model from the same maker in 1.5 1.6 1.85 (about 5,6, 8*) facings. I find the more open one more flexible and comfortable, but top players could not get a sound out of it.