Now that the smart bellybutton answer is out of the way, here is the real answer(for most industries).
Inside sales does not really generate sales, they simply recieve orders. Now they CAN increase the size or value of an order, through salesmanship, but as a rule, they do not attempt to generate new customers, rather they service existing accounts and call in orders.
Outside sales must generate new customers, often from cold calling or speculative sales work. Once they have accounts up and buying, they work as a liason between the company and the customer, keeping everyone happy.
The important info:
Inside sales:
Non-exempt employee, generally makes over time.
Usually salary, sometimes with a taste of commision.
Generally no expenses or vehicle included in package.
Usually very little travel, other than to continuing education seminars or tradeshows.
Outside sales:
Exempt employee, no overtime pay.
Usually a small salary, most pay from commission.
Expenses and vehicle usually provided.
Often a lot of travel, local, regional or national, depending upon the industry.
If you have sales experience, go for the outside, for sure, if not, work inside and get some idea of what sales involves.
