ABS and ASA both sit in the “needs a hot bed and an enclosure” family. Heat deflection is similar. The difference shows up after months on a balcony, a car dash, or a roof mount in Beirut sun.
What UV actually attacks
ABS gets its toughness from butadiene rubber. Those double bonds break under UV. The part chalks, yellows, and then cracks at corners. ASA swaps that rubber for an acrylic ester. Same family of print settings, far better weather face.
When we still sell you ABS
Indoor housings, paint-over parts, and anything you will acetone-smooth and keep out of the sun. ABS is usually cheaper and plenty strong. If the brief says “on a wall facing west,” we steer to ASA.
Print notes from this shop
Bed 90–110°C, closed chamber if you have one, dry the spool. ASA warps a bit less than ABS on parts wider than ~150 mm, but it still lifts if the first layer is cold. Ventilate — both smell.