For me, the yeasts themselves are similar enough between the two that I make my purchasing decisions based on the packaging. White Lab vials are reusable and recyclable. My homebrew shop has a bin where they collect used vials, so there's less of a chance for waste using the vials vs. the Wyeast packaging that ends up in the trash can. On top of that, the vials are cool and my 3 year old loves to keep them to store tiny rocks, twigs, bugs, or anything else he finds outside. They work great to make small popsicles as well. So when I use liquid yeast, I go with White Labs, unless I'm searching for a particular yeast they don't have.