Blackrock Portfolio Analytics Group or Archelon?

I got offers from both Blackrock and Archelon, and both of them are for co-op positions (so basically two working semesters). So I am just wondering, how well known is Archelon? Maybe no one knows about it at all? I think I will probably enjoy Archelon more (from interview experience, and job description), but I think Blackrock has way better name recognition. But I am interested in trading, and Archelon is a small trading firm, so I feel like I get to learn about stuff I am interested in. So what would you do? Pick a well known firm doing something you are somewhat interested in, or go with a smaller (maybe not well known) firm but doing something you think you will love?

Of course, I have to take the full time interview process into consideration. Having Blackrock on my resume will probably make it a lot easier to get offers for fulltime positions.

Any comment is greatly appreciated.