Both series have an animal-girl female lead and a (relatively) smart human male lead. There really isn't much else to add, but I honestly believe there is no need. Simply, if you liked one of those series, you could try the other one too.
Considering that both series share the same author, it not surprising that they also share a number of themes. Both take place in a medievalish setting, both feature a clever male lead and a juujin female lead. Simply put, with this many similarities all over the place, chances that you will like one if you liked the other are rather high.
There was something in Maoyuu Maou Yuusha that reminded me of Spice and Wolf a lot, the problem is: I'm not quite sure what it was. Maybe it had something to do with the medieval setting or powerful, non-human, ageless female lead or maybe with the semi-educational undertones (trading in Spice and Wolf and multitude of different things in Maoyuu Maou Yuusha). If you liked Spice and Wolf's uniqueness, then Maoyuu Maou Yuusha should prove itself to be a good read. On the other hand, if it's Maoyuu Maou Yuusha what you've read, then you should definitely try reading Spice and Wolf.
Teiichi Niiya is a first year middle-school student at Seikyou Private Academy, an institution known for mysterious occurrences. The boy quickly finds these rumors to be true when he meets Yuuko Kanoe, a beautiful, mischievous girl who quickly takes a liking to him... and happens to be a ghost who seemingly no one else can see! Unable to remember anything about her past, Yuuko enlists Teiichi’s help to discover the truth, and together they join the school's Paranormal Investigation Club. With fellow memebers Momoe and Kirie, the pair will investigate the many strange happenings around campus, including the shadowy circumstances surrounding Yuuko’s death.
Both series feature a mischievous (and playful) female lead who not only loves the male lead, but also loves to teas him. If you liked the female lead in one of those two series then you could give the other one a try.