While it is true that the rules are the same just about everything else is different from the pace of the action to the ability to physically interact with your opponent. Well I think first off we need to remember that online poker and live poker are in fact two different games. Many of these people think that a HUD breaks with the tradition of the game which includes reading your opponent and making gut decisions.
This is a common complaint that I hear from those who are more let's say 'old school' about the game or those who come from a live background. I could go on but I think you get my point. How often they fold to a continuation bet on the flop.How often they make a continuation bet on the flop.Think about how having the following data in front of you might help you make a better decision in a key spot: Information is power though even if you only make limited use of it. In fact for people just starting out at the lowest stakes I recommend a very scaled down bare bones HUD so that they focus more on the fundamentals of the game instead.
You don't even have to pay much attention to it if you don't want to. All a HUD really does is give you some extra options (information in this case) at the tables. But if you were to play against somebody who is equally as skilled then this advantage that they have might be difficult to overcome.