How easy is it to move your data from a shared host, to the exact same host, just to a full server? What about switching hosts?
In both cases, some hosts will be willing to do the job for you, so it'll be pretty easy then.
You can do it yourself, and it's not particulary hard, just that it can be labor intensive.
I think shared hosting is the right bet at this point in time, but since it is a business you're looking hosting for, try to stay away from cheap hosting. Get business grade hosting, at business grade prices.