While the 10w-30 will have less VII's and therefore be more stable and have a tiny bit more of most other additives(dettergent, anti wear anti foam etc) due to the extra "room" now created in the formulation.
nothing is free in a formulation and teh better start-up of the 5w-30 is bought at teh expense of otehr things.
Short of a brutal winter, I see no reason to ever run a 5w-30 over a 10w-30.
Rick, go with the 10W30. I am switching back to 10W30 from 5W30 in my Explorer because 5W30 thins out too quickly.
Check your personal messages, I sent one a while back that you have not read yet. -Joe
Assuming the same brand of oil, with approximately the same additive package, there might be a small difference at operating temperature, but probably not enough that you would ever notice.
The 5W- will pump up faster than the 10W-, particularly in extreme cold.