Portable vs On Board Air Compressor?

I plan to do a good amount of beach camping and light off-roading. I'll likely be adjusting both tires AND airbags somewhat often. So like I said, don't mind doing a little extra work to save cost. But is a portable really THAT much more of a pain that I'm going to be kicking myself if I don't get an on board?

Also, I don't understand why an onboard comes with a tank and a portable does not.