Everyone's personal preference is different. Take me for example, having 36 band size and fairly wide breasts the medium cups got used twice then I put them back in the box and gave them to another noogler a few months ago because they we so narrow on me that they were uncomfortable to wear and actually hurt, so I jumped right into the L's. After a few months of the L's even though my natural size is still small my swelling started outgrowing the L's so I bought the XL's. Now I can still use the L's, and did quite often when I went out because the XL's are to big and bulky to wear while driving, but they cracked and I can't afford to buy new ones so I just use the XL's all the time now, which came cracked and are getting worse so I'm going to have to brake down and buy some more when I can afford it because the tape and glue isn't working very well to keep them from getting worse. I'm still only a 36A without swelling, but I achieve anywhere from a 36B-C with swelling and fill them almost half way. I achieve really good swelling, the growth is just slow. Lots of others will tell you not to move onto the next size until you've outgrown or almost outgrown the current size, but personally I don't think there's any real "rule" that says you can't upsize if you want. Just remember that the larger you get the larger the diameter, so unless you've got a band size and breast/chest shape that will support the larger diameters you may have a problem achieving and maintaining a suction. That's one problem I've never had, I guess I was just built for noogling, doubt I'd have much luck with the XXL's though, I think they're way too big for even my frame.
The main thing to think about is what you're looking for in growth. If you've got nice round boobs and are looking for outward pull and growth the smaller sizes are better for that, although the L's work pretty good for that too. If you've got more tuberous shape breasts than the larger the diameter you can work with the better if you're looking to achieve a more rounded shape, because like the XL's seem to pull and grow the tissue in a wider/rounder shape before you see a whole lot of outward (sticking out) growth. Where I'm looking for I guess a bit of both, so I was using the L's and XL's till my L's cracked to where I can't use them any longer, so I'm just using the XL's now. They do give me nice swelling and shape though, so I think I'll just stick with them until I reach my goal. The main thing is that with the larger the cup you use the more you have to be careful not to over pump, this is especially important with the XL's, as they seem to be easier to over pump with without knowing you are than any of the other sizes because it takes more pressure to achieve and maintain a suction and doesn't seem to cause as much discomfort and pain as the smaller ones when you have over pumped a bit.
Hope this helps and didn't help confuse you any more than you may already be. ???
