My dog is clipped to the seatbelt on the back seat.
I've had a couple of occasions when, because I've had to have the back seat down for carrying bigger loads, she's had to sit in the front passenger seat and she hates it; thankfully, it's only ever been on short journeys.
In the back, she's comfortable. She can sit down and relax and sometimes she'll fall asleep.
In the front she seem aware of every movement of the car and it like she feels less secure somehow. She certainly wouldn't fall asleep as she sits up the whole time and seems to be almost gripping the seat.
Having a dog sitting beside you like that can be very distracting as well, even if it isn't trying to climb onto your lap; you're just too aware of it and what it's doing.
Much better to have the dog in the back, restrained in whatever way you chose.
Highly unlikely they're going to be getting up to anything, unless the restraining system isn't secure.