Ipe has a lot of facilities aimed at users of the LaTeX text layout language that is often used in academic work. If you know how to work with this language, you can do things such as add complex equations directly into a diagram, and Ipe has facilities to make sure that the fonts in your diagram are consistent with the fonts in your document. It also has a stylesheet capability, so you can set attributes such as fonts, colours or line types and carry them over between drawings.
Krita is generally regarded as the best bitmap art package on Linux and possibly the best free and open source art package on any platform. Having these features is a boon, but the real power is that you only have to click on a bitmap layer and all of the bitmap drawing tools can be brought into play within the same project as the vector elements, a fairly unique advantage. Krita also has a suite of image processing tools, although their integration, while certainly useful, isn’t quite the slam dunk that the integration of vector and bitmap drawing is.