Alan,
When towing, the torque figure is more important than the bhp - assuming the bhp values are roughly similar - which they are.
Look at the brochures and see if you can find the torque curves for the engines - a higher torque and a wider flatter torque curve are important.
After all you don't tow with the engine screaming at max revs and max bhp - but you will be trundling along the motorway at 2000 rpm with the car in top gear - and this is when more torque helps you to maintain speed, not change gear on inclines, etc.
Ford or GM? Choose the one you like best from the inside - seating, driving position, comfort, leg-room, passengers view out.
Interestingly, two years ago there was an article in Car magazine that compared the cost of buying a new Ford Mondeo or GM Vectra, running that for 4 years, compared to buying a 6 or 12 month old "premium" car - like Volvo (Ford), Saab (GM), Mercedes, etc.
The purchase costs were similar, the running costs were similar, the people interviewed preferred the premium car, the premium car was worth quite a lot more after 4 years, and consequently the total ownership cost was lower. Just a thought.
Robert