SQ has IMO lost its polish in a big way. The three versions of the long haul seats are too hard and the leg rests are inadequate - on two versions the only rise to 45 degrees which is useless. The crew are not what they used to be either. I think SQ trade on past glory.

OTOH, I see OZ as a rising star. The seats are good, the food is good and while the crew are not perfect they are willing, responsive and helpful. LO offer a very solid product which does what it claims to do, they're not five star but the seats are fine, the crews responsive and the food usually very edible.

I would choose the latter without thinking for long and you would also get to avoid a transit of FRA which is always a good thing. It's probably the worst European airport to transit.