10W30 is fine for most climates. If you live in snow country and drive short distances, then the 5W30 might give you better lubrication during all those cold start ups.
When I lived in the Boston area, my cars had no problem starting with 10W40. I never worried about oil grade and temperature.
I run 5W30 full synthetic in my 89 3sfe. It works fine with minimal oil consumption, mostly due to a few small external leaks. My car has 64K miles on it. I drive it a lot so the oil is changed every two months (about every 4k miles).
I think people get carried away on these oil decisions. The enemy of your engine is sludge. Cheap oil will have more sludge forming chemicals in it than the best synthetics like Amsoil, Repsol, Spectro, etc.
Those high end oils can be expensive, but stand up better to long oil change intervals like I do. For me, top quality oil is cheap compared to the labor for a service station to change it. With 2 jobs and night school, I don't have time to DIY.
You can get similar results with cheaper oil like Mobil, Shell, Chevron, and Valvoline dinosaur oil by changing with a new filter every 3k miles.