No UHT is just Ultra Heat Treatment. It's a form of pasteurization and has nothing to do with fresh or reconstituted milk.

There are typical 4 type of pasteurization.

High Temperature Short Time, Higher Heat Shorter Time, Ultra High Temperature and Ultra Pasteurized.

That's the purpose of UHT, to reduce the dependency on refrigeration.

In the end, it boils down to personal preference but nutritionally either pasteurization method produces similar quality only the taste differs.

The difference in nutritional seen is mainly due to milk sourcing rather than the process. Eg. it is cheaper to source overseas as they have huge production and well established processing and logistic so that milk will end up as UHT. UHT is also suited for long distance transport. This is just an example, but there are tons of condition being taken in logic that end up in the product.

Not all cows makes the same nutrition content. Company like DL source their milk from around the world, and the nutritional values showns are the average given . Both are still fresh milk just their source is different hence the nutritional values is different. Nothing to do with pasteurization method and if any is very minute.

Full cream milk is reconstituted milk, and during processing they are added more milk proteins or milk fat so that it taste more lemak. So may even add lecithin which will thicken the milk and improve mouthfeel (so feel more kaw or lemak). And also added vitamins to compensate.