Agreed on Aasimar, however, the best one for Optimization is....
Kobold.
I didn't think so at first, but after taking a Kobold Bard up to level 11 so far, sweet jesus is Pack Tactics and Grovel overpowered. The -2 Strength is largely irrelevant thanks to Finesse weapons and Medium Armor.
Honestly, even in a relatively open world campaign like Storm Kings Thunder, the sunlight sensitivity rarely came up. DMs simply don't have the brainpower to factor that in, so most never cared, which means woohoo Advantage almost 24/7 in game play. I could drop upcast Inflict Wounds like it was going out of style with little worry about wasting a spell slot.
The Grovel is also amazingly OP for boss fights. Providing Advantage for ALL targets while NOT granting Advantage against yourself is pretty impressive, especially once you pickup Bonus Action attack abilities like Animate Objects and Bigby's Hand. With Grovel + those spells, I can solo bosses pretty easily.
Lastly, the -2 Strength is very easily compensated for because Strength has the most "set value" magic items. One Gauntlet of Ogre Power later and that significant detriment to the class goes away.
OH, and it's small sized (so moving through Large enemies) BUT doesn't have 25 movement speed reduction.
All in all, unless you have a DM who is hyper focused on Sunlight Sensitivity, the Kobold allows for stupidly good optimization.