Oi everyone,
Most basic information about tieflings in Faerun. Describing some things of which many around seem to forget, don't know or simply ignore. Source is the official WoTC supplement for Faerun campaigns "Races of Faerun". Underlines dedicated to DiceyCZ.
Tiefling
It is rather plainly stated that Faerunian tieflings ARE TAINTED by their EVIL heritage (in blood and soul), and although not restricted to evil alignment, have to struggle with their nature when trying to be good.
Aasimar
Less strong indications and details here, thus more space for interpretation. While obviously inclined towards good and extraordinary beings, Aasimars seems to be less bound by their heritage overall. I would say perhaps its because of their good nature not forcing it as much as evil one does on tieflings. Similarly to the latter Aasimars can be frowned upon and shunned. Even if reactions are less severe in general its good to remember that.
Cheers!
P.S.
Wasn't sure where to put it, so it lands here. Sorry if its not the right place.
Per request I'm adding Aasimar.
Also pardon me my poor english.