Crunchy differences:
A few extra class choices (If you wanted to try a Basiran Dancer rather than a bard, or a Spell-singer (sort of a sorceror, but can cast spells in armour), you could ask your DM about those choices.
More feat choices (and the skill choice Pantomine). More Knowledge choices on the military side.
Slightly different subraces. More spells.
The world itself (unless the DM wants to ramp it up) tends to be low-magic. So after adventuring for a while, you won't find too many player character race types that match your level (there will be a few, but they won't be thick on the ground).
Roleplaying-wise, the cultures are detailed and interlocking. There is a mighty emperor, and he is seeking to expand his domain rather aggressively. Also, the gods take a VERY active hand in human affairs through their churches. Also, many countries practice slavery.
That's my top-of-the-head stuff. Hope it helps.
