No doubt about it, the slim beauty is the way to go. It has a low profile, is easy to tie once you get the hang of it and is nearly 100% in breaking strength. For class tippet, I prefer 20# Mason. It is stiff, for good turnover, and has a large diameter, which means good abrasion resistance. And if you are into IGFA requirements, it is easy to come out with the maximum length of class tippet. Impossible with double biminis.
And for the record, biminis are not that hard to tie. I tie them to relax. Easier than yoga.