High pressure boilers produce high pressure steam. If you need high pressure steam, you have no choice - you must have a high-pressure boiler. So you are asking the wrong question. You should be asking what are the advantages of high-pressure steam over low-pressure steam. And even then, it is generally the case that one does not choose high-pressure over low-pressure based on 'advantages' or 'disadvantages'. Instead, the choice is dependent on the needs of the process. For example, if the process is simple and requires steam only as a means of conveying heat from the boiler to a single point in the process, and if the amount of heat that is required can be met using a low pressure design, they that would be the choice since it is likely to be less expensive. Often, however, the process is more complex and requires heat at multiple points and at multiple pressures. In that instance, generating high pressure steam and then throttling it down through a series of stages of the process makes more economic sense.
