Tiefling or Aasimer???

[Barehander]

Well, Races of Faerûn certainly doesn't suggest they're overwhelmingly evil or anything on par with Drow. Evil Aasimar are specifically mentioned twice, and not as a rarity, too.

[Ebok]

Efu tends to be Evil bias due to it spawning from an overly good bias server. Evil has more freedom for plots and new ideas and new conflicts, so by a rule of thumb you can imagine if it says you're normally evil. It'll be always evil in efu.

Fallen Good things tend to instill more thumbs up, though again, its for the DMs to decide based on what you're doing with these things.