Ao no 6-gou, Armitage III Recommendations
Although dealing with completely different subjects, both animes have a nice mix of action and things that make you think about; both are (somehow) sci-fis. And: they are on a similair graphical level (although Blue Submarine No. 6 sometimes uses CGI in a not too skilled way).
By the way: both animes exist as single movies and 4-part OVAs.