Vote selling uses your VP and it votes on other people using your account until a vp threshold is met, let's say 80% and then it stops selling until you reach 80% vp again which shouldn't be an issue since you will not be participating much anymore but it gives you flexibility, because you keep all your sp and can vote and reward things if you want to manually.

Delegating, if you delegate all your sp to a bot, you won't know where your sp is used and your vote value will go down to most likely 0 because all your sp will be delegated, it takes 7 days to recover delegated sp after you undelegate it and with vote selling you can configure it and change it around every time you want and make it stop or run again anytime you want without delegating your stake away.

If you are interested in smartsteem, I would love it if you used my referral link <3