Gunslinger Girl, Haibane Renmei Recommendations
Both series are of similar nostalgic feelings. Problems that they are showing are difficult to assess. Very ambiguous. Both anime are also formally similar (colors, the pace of action, universal message).
Although the topics aren't the same, they have an extremely similar emotion to them. If you liked Haibane Renmei, you'll surely enjoy Gunslinger Girl.
As another user said, there is a certain emotion one feels for the girls. As you watch you feel sorry for them yet enjoy that they can still manage to find happiness from day to day.
The premises of both series are, at their most basic level, very similar, if not identical – a cast of predominantly female characters are essentially “reborn” into a new way of life, with no recollection of who they were previously. The girls in both series experience similar emotional and existential dilemmas. In general, these are series in which drama and atmosphere take precedence over action.
These two shows deal with similar themes, including mortality and the loss of memory. The girls in both have a gentle innocence about them, though Gunslinger Girl's are marred by their purpose as tools. Excellent series to compare and contrast because of this.
Minus the occasional action in Gunslinger Girl, these series have a very similar tone and cast of characters. Gunslinger Girl and Haibane Renmei are more soft and subdued series, where the quiet moments are often the most powerful.
You can compare anime by mood or by plot. If you go by mood, Haibane Renmei and Gunslinger Girl are very similar. Both have the slow-moving, heavy-thinking setup that makes you ponder moral questions. The plot, however, could not be more different.