its personal pref. really.. You will soon learn some jumps are better for each spin. If your regular it may be easier to spin backside on a jump that is angled skiers right and frontside on jumps to skiers left.
That said, I tell all my buddies that are trying to get into spins the same thing:
"Learn to ride switch well... its a much more important skill and will get you further in snowboarding and make learning spins far easier when you are comfortable riding your board both ways."