I would say the shorter the message is, the better chance somebody will leave a mesage.
Your voice mail would be
This is so (your name). Please leave your name and number and I will return your call as soon as possible.
in a very nice tone.
Only a few words less than your first option. But, you save the caller several seconds. You don't have to say your number, the caller already knows that. You need to identify yourself so the caller knows he did not dial a wrong number. You need to say you'll call back as soon as posible so that he knows it won't be too long before you call back.
Consider the caller may be a hiring manager, he would have to make tens or even hundreds of phone calls. Short, clear and nice message would let him have good impression even he has not talked to you yet.