You can't look at just the motor. You have to look at the size, ride etc. The Ford has the bigger crew cab. The cummins is an awesome motor, but the new 6.0L PSD is a good motor as well.
I am on my 2nd Ford and will always own one.
My toy hauler weighs 12,000lb going down the road and my truck pulls it great.
The cummins would do just as good of a job.
I had 47,000 miles on my 02 PSD, about 20,000 of that was towing, ran great the day I traded it in, only did normal maintenance.
Test drive both and see which one you like.
Ford has major changes coming on the super dutys for 05. Go to www.thedieselstop.com to get an idea. If you like leaf springs, you better get an 04 or older.