Few reasons why this might happen. 1 User error and 1 because of the screen.
1: User error: Make sure in settings under 'Display' you have the font size the same on both devices.
2: Screen technology. Now I know the Nexus 7 is larger in size than the Galaxy Nexus, however, the screen is very different. The resolution on the Nexus 7 is 1280x800 where as the Galaxy Nexus is just under 1280x720 (something like 1197x720). So there are extra pixels to play with. ALSO, the Galaxy Nexus is using a Pentile display, rather than the normal RBG layout of the IPS LCD that is used on the Asus tablet. This means, There are more subpixels per pixel on the device. This also means, that the Nexus text is not going to be as dense in pixels/detail per pixel per inch of the device compared to something with an RBG layout. This could cause the text to be slightly more bloated compared to the Asus Nexus 7.
I am not an expert on screen tech, I am doing all this math based off of what I've read in the past. So if anything I've said is inaccurate, feel free to call me out! lol But I think that might be contributing to the issue.