What's best, Skins or 2XU tights or other?

If they are all made from the same material - then they are all the same and then the only difference is 'fit' , price, and how good they make you feel on and off the track . Especially if you wear them on a date like some contributor did here a long time ago.
If they are are really good they will have the carbonised fabric. Go for local made, at least you are supporting Australian workers and business - there are other Australian suppliers - try googling compression sports wear in your local area