Actually, the new, synthetic SUDT is also now out. I understand it is not higher priced than the older version it replaces.
The difference is similar to using plain, 10w-30 dino oil in an engine versus 5w-30 Mobil I. There is a price difference. Both will meet specs and neither would void a warranty. Ditto with UDT and SUDT. You pay your money and you take your choice.
I personally prefer SUDT for its superior cold/heat protection, but UDT is just fine. The world isn't going to end because you might choose one or the other.