My buddies Scale Race II ( a plain Bearing or Fox 15BB varient of Scale Race) is 2 tenths a second faster around the circle with a spinner than without. 140 laps per race, he uses the spinner. Course if you ding the prop on landing you loose everything pulling the prop, but a clean race saves you 28 seconds and THAT is a lot in any race. Multiple tests with different props, this was the average.

If you're not racing though, it's merely an opinion of looks and ease of operation.