Depends on your current lenses and filters.... you would want to have a lens with equal or greater filter diameter than your current lenses if you don't want to buy additonal filters. I am not talking about UV or clear filters, which I don't use.
Larger filters cost more money than smaller ones. Larger filters can be fitted to smaller diameter lens filter mounts using step up adapters which are only a few dollars.
People should post 100% crops, wide open at different apertures under different lighting conditions. Just about any lens will produce very good to excellent results stopped down. I think that it is a given. I'm interested in f2.8, otherwise why bother buying and paying for an f2.8 lens.