This is just my opinion,and is not from actuall knowledge of both as i have only been mobile.
But if you are refering to running your own salon or going mobile, i would say it is harder in some ways to be mobile as you dont have a shop front it takes time to get yourself known and work can be irregular and you cant pack as many clients into a day as you have to allow for travel and setting up time.
But mobile is great you can do hours to toally suit you and there are very few over heads. xx