I have one, a B200 Turbo, as my daily car and contrary to everyone's posts, I think its a really good car especially for city driving.
Can't say much about the B170 but since engine is very basic, many people will probably think its overpriced. About its light steering, while it feels kinda weird at first, you'll actually get used to it quickly. This is now one of my favorite aspects in that car.
Here are some things I like about my B-class:
1) Raised seating position for better road view
2) Large windows for visibility
3) Fun drive with the turbo engine
4) Very generous legroom and boot space but exterior size is very compact (good for city driving)
5) Light steering that gets heavier as you gain speed
6) Nice interior ergonomics. You don't have bend much when getting in and out of the car.
6) Ipod integration very good
7) Unique and cute in a somewhat understated way
Of course, no car is perfect so here are some of my complaints:
1) Some minor quirks (power windows, handbrake sound) which is being addressed by the dealer
2) Suspension somewhat harsh (for sport version) typical in a small car
3) Side view mirror visibility not the best
4) Aircon not as strong as Japanese cars
I guess the bottomline is, it'll really depend on what you and your dad will be looking for in a car. Good luck on your car shopping!