Bi-lingual site

My client wants to a Spanish version of their current English site. My question is a procedural one.

Is it better to go with something like WPML, or to just make a subdomain for a second Spanish site? We expect the Spanish site would be a bit simpler than their current site (~40 pages). My experience with WPML has not been great and I’m wondering if just creating a second site might be a reasonable solution. For the latter option, I recognize that each site would have to have its own media library and theme support files.