Product Variant

Hi everyone, I was wondering your thoughts on variants?

I have products that come in 1 oz/30 ml, and 2 oz/60 ml and I have about 400 products. I currently only have 400 listings of the 2 oz, and the size is in the item details. I’m wondering, should I create 400 more listings for the 1 oz and keep them separate, or should I just make the variance for the existing products? Also, as a consumer, what sounds better in terms of beauty products? 1 oz/2 oz or 30ml/60 ml?