I would choose OZ, the seat is better than any of the current SQ long haul seats and while not the most polished service the crew try hard and the food is usually pretty good. The connection will be OK and obviously protected in the event of a problem.
I dislike all three current SQ longhaul seats although I would say the one on the A350 is the least worst it's still uncomfortable as a seat - too wide and too hard. I find SQ service very mediocre these days - complacent crew who are inflexible and impersonal in their approach and keen to tell you how good they are while you're sitting thinking you would rather be flying with another airline! I really don't see SQ as an airline who I want to travel with these days and that's after using them for 20+ years, they are going down badly.