Amber C. posted the definition of each show, in reality there can be some variation if a models works multiple rooms or sites, but it is basically as described. For example a model may be pvt with you on one site, and do a show on another, is unethical but common. Similarly, if you ever have a model working with someone else, you may need to make both happy for a show. Generally things are pretty straight forward though.
I suspect what the OP was asking is why pay more for the more exclusive options, when you get the same action? It is a very different experience for a group show, compared to a public show countdown/ gold show, compared to a pvt or true pvt experience.
In simple terms a public show is usually a fairly planned experience, group is unplanned but a model usually has to decide what is the best show for that group (the group may suggest what they want, but the model must choose), a regular pvt has watchers, a true pvt experience is just you and the model.
You can sometimes get a bargain, like a model will let you hold a group show as pvt, but if you can afford pvt and look for exclusive time in group, it is a bit cheap. Keep in mind a model is not an object, you wont get her best if you lack class. The best experiences are in taking the exclusive options so long as you can spend for the time, rushing the pvt experience I feel is a waste of time and money. I would plan for 20 minute minimum exclusive time, otherwise choose another option.
As for the differences they can be pretty extreme. Exclusive times can be very personal, and extra sexy, sometimes you get lost in the experience as though you are there, something that will never happen with the group experience.
