S40 Editons have different versions. Each version supports set of JSRs. But under each edition, two devices can support different sets of JSRs. So there is differnce. So we can do the testing on device to make sure app works on both handsets (There is a possiblity it will not).
In S60 SDKs we have different editions, So for a particular edition S60 X Edition FP-X, we will have 'x' number of devices. Now here is it similar to Java platform that, under particular edition device's support for C++ APIs might be different. Or the app developed on particular edition will work on the all the devices under that edition?