Both series are distorting two literary classics. Miyuki-chan in Wonderland the two works of Lewis Carroll (Alice in Wonderland and Alice Through the Looking Glass) and Ikkitousen the Chinese classic 'Romance of the Three Kingdoms'.
Miyuki is well reflected in the intent of referring to books, while in Ikkitousen is just one mension that is heard only rarely.
Both series are inspired (more or less) by "Alice in Wonderland". Thought Miyuki-chan In Wonderland is more like Ecchi version of "Alice in Wonderland". While Pandora Hearts is Shounen, which contain also element from other titles, like for example "The Wizard of Oz".