UHT is a process that uses temperatures not lower than 135‹C for at least 2 seconds to kill all bacteria in milk. The milk is then packed in an enclosed, sterilised environment. It can be kept for 10 months at room temperature if the pack is unopened.
Pasteurised milk is processed at temperatures not lower than 73‹C for at least 15 seconds, then immediately reduced to 4‹C and maintained at that temperature until consumed. It kills only the pathogenic bacteria (bacteria that make you sick). Because of this, pasteurised milk has to be kept refrigerated all the time (even if unopened) and its shelf life is short (4 weeks).
Sterilised milk is treated with a temperature of not lower than 100‹C heating for a length of time. Since it is packaged in bottles, additional treatment of the bottles is required to ensure the sterile condition of the product. As a result, the sterilised milk can be kept for 8 months (if unopened) at room temperature
All liquid milk is equally good and delivers the same nutrients that fulfil growth requirements. Your choice very much depends on circumstances such as convenience, preference in taste or storage choices that you prefer.