This is an important feature to some but it seems no one ever mentions it. Are both sims active at once, receiving calls and texts on both, or do you have to switch Active SIM and Standby SIM in the UI? Can both slots access LTE Data or just one slot, as is much more common?
That's what I want in a phone, support for Both a Tmo and ATT sim that can Both get LTE data, even if you have to switch the active data connection manually. Tmo is much faster in some areas and ATT in others, so I want to be able to switch active data on the fly.
To me that is even more important than being able to receive calls on both lines.
You can sort of use both at the same time. The phone's software allows you to select which SIM is prioritized for data, calls, and SMS. You can choose one SIM for calls and SMS, and the other for data, or any combination of the three.