What I like most, as I read from the beginning (I'm halfway through Origins), is how organic it all feels. The heritages, cultures, and such have a real narrative feel, not the bags of features of O5E, half of them crap. Every feature in A5E, even those that look more limited than O5E type origin features, clearly has a purpose and will be useful at some point. Many features are clearly designed to fit well with particular classes, too, or to supplement a "non-optimal" or "non-syergistic" class. The classes I've looked at have a similar well-motivated feel.
Reading O5E, I felt I was struggling to find combinations of race/class that fit my concepts for characters. With A5E, I find that every new section I read inspires multiple new, realizable concepts i hadn't even considered before!