Is it always better to contact a named agent...

When I sent submissions to an agency that required me to send the submission to a submission department, and I thought one agent there was an especially good fit, I would mention that in my letter. In one case, I suggested one agent in particular, and another ended up asking for a full, so expressing a preference did not knock me out of contention with others.

I'd double check -- some agents won't read direct queries when their guidelines say to send them to a submissions email address. The person going through the submissions will generally direct your query to who they think is the best fit, though I see nothing wrong with doing what LKP did an mention a particular agent.