The front wheel bearing can be discounted with the following test
Jack up the car, and squeeze the piston back into the caliper so the pads are not contacting the disc.
Put the wheel back on, and spin the wheel, it should rotate freely, and if you place your hand on one of the coils of the front spring, any roughness in the wheel bearing will be transmitted to the spring and will be able to be felt.
Unless proven otherwise, a sticking brake caliper, be that caused by poor fitting of brake pads, a defective caliper, or indeed a flexible hose that is breaking down internally, restricting the brake fluid return would be my first thoughts.
You can of course drive the car for ten miles, come home and feel the comparative temperatures of the front wheels with the back of your hand, a tight wheel bearing is unlikely to result in a major temperature differential between the two front wheels, and would be howling in protest if causing the type of drag you suggest.
However I would be highly suspicious of a diagnosis of a defective gearbox differential, this sounds like the mechanic is either clueless, or aiming to wipe your eyeballs with an expensive or unnecessary repair
Let us know how you get on please
Brian
