You prefer fresh-squeezed because it's neither oxidized nor heat-treated. Squeeze an orange into 3 beakers and let the juice stand for 1/2 day, a day, and 2 days; you'll see that it loses the appealing brightness and floral notes quickly.

Related:

http://www.cookingissues.com/2010/10/01/fresh-lime-juice-wtf...

Note that whether or not it says "from concentrate", this process is still happening. If it wasn't, they wouldn't be able to screen out pesticides and bacterial agents, and wouldn't be able to keep each jug to the correct concentrations of its component chemicals (which each have very different molecular weights, and so would band in industrial mixers) and so forth.

If you mean that you prefer actual juice you get by juicing an orange yourself, then sure. But "fresh-squeezed" orange juice at the supermarket is just organic synthesis without a freezing step. (Which is an important-enough distinction; freezing fruit, or its juices, denatures a lot of the nutrients.)

It has its upsides and downsides. When you are attempting to maintain a brand consistency of flavor is important. That requires a lot of processing. If someone is literally squeezing some oranges and giving you the juice, the flavor will be slightly different every time.

> I do know that I far prefer the taste of fresh-squeezed (and, in fact, won't buy anything that is not). But I never really knew why.

Honestly they should just forbid using the images of fresh fruits on the cover of their fruit juice packs. That's just a gross lie compared to what the contents is made of.