[dg7feq]

I would say there are three main reasons to use a dual sim phone-

1) use your personal and your business SIM in one phone to avoid carrying 2 handsets and
2) optimize your cost either domestic or on roaming by having a 2nd SIM (e.g. one with good voice tariff and the other with good data tariff)
3) roam with your domestic number for availability and use a local SIM for cheap data/calls.

So yes, your thoughts are valid...