A camera is far faster in "startup time" (there's nothing to start up, just press the shutter to take a photo). And a DSLR will outlast battery life of a phone at least 100x.
No, the DSLRs can be left permanently on. It consumes nearly no battery in that state (a single charge will last many months) and yet it's always ready to take a photo as fast as you can grab it.
A camera is far faster in "startup time" (there's nothing to start up, just press the shutter to take a photo). And a DSLR will outlast battery life of a phone at least 100x.