What is the difference between the Bach Strad 37 and the bach strad 43??????? is one better? or are they used for different things?

I think the "37" and "43" denote the bell design (diameter/taper), and the bore size may be a little larger on one than the other, but I`m not sure which. Logically, I would expect the "43" to have a slightly larger diameter bell and slightly larger bore, but can say that`s a fact.

I just also thought that you might find out all you want to know by going to Bach`s website, or maybe www.trumpetspot.com.