Both Maple 13 and 14 are actually using the same fonts. The difference is in the interpretation of "Default" for the Font Antialiasing setting in the Options panel. In Maple 13 and earlier, a setting of "Default" meant "Disabled" for most cases (the main exception being Chinese and Japanese versions of Maple, where font antialiasing is needed to render the characters legibly). For Maple 14, we've enabled font antialiasing as the default for a much wider range of systems.
Why the change? The font antialiasing algorithm used by releases of the Java runtime that were available when we shipped previous versions of Maple had some weaknesses. Among the most egregious of these was that the diagonal stroke would disappear from the italic letter "z" or upright numeral "2" when rendered at certain point sizes -- clearly not an acceptable situation for mathematical software! Fortunately, most of the problems have been resolved in the Java runtime that's distributed with Maple 14, so we're finally able to enable font antialiasing as the default configuration.