I am looking for a dual SIM phone, that will allow me to receive calls (not simultaneously of course) to both SIMs without any manual switching. From what I have seen Android 4.0 seems to support voice call for SIM #1 and video call (which seems to imply voice too) for SIM #2. That seems like you get 2G voice coverage for SIM #1 and 3G voice coverage for SIM #2. Is this true? I guess this may vary depending on particular phone model, but what solution is Android dual-SIM industry mainstream currently?
Please take a look at this question and my answer to have basic understanding on how the manufacturers use the terminologies.
These differences are hardware based and nothing to do with Android. Hence, if you had properly chosen your hardware:
I am not sure about your other question about video call.
Update: In Samsung Galaxy Y Duos (a dual SIM phone) though both SIMs were active to receive calls and access Internet simultaneously, only one of them was allowed to use 3G network. If I opt for 3G network in SIM1 and opt for 3G on SIM2, a message says I can't use 3G on both and changes SIM1's network to 2G and retains SIM2's network to 3G as per my input.