Design Science licensed MathType to Microsoft in 1991, with Microsoft calling it Equation Editor. According to Design Science, there have been no additional improvements to the MS Equation Editor since 1991, while MathType has continued to evolve.
I have no way to test this here, so Peter may be correct about the graphics.
If not graphics, then equations read from Pages in a Word document would find no matching font support and potentially appear as jibberish. If however, you were to install MathType for Mac, it would install mathematical fonts, and remain a superset to the equations introduced into your Word document, whether by MS Equation Editor, or through compatibility with the Windows version of MathType.
MathType is about $99 retail, and $50+ for students. There is a 30-day trial and afterward, MathType transforms into the free MathType light and all mathematical fonts remain installed. MathType when installed, becomes part of the Pages menu infrastructure for ease of use.
A link to their FAQ page is here.
If you upgrade to pages 2013, all equations will be completely stripped out of the document. There will be not even be an image of the equation.
If you create a document from pages and export it as a .doc or docx then the equations will also dissapear and leave behind a blank box.
I found no way out of this.