Coverage of a desk mounted 205H should not be significantly different from a ceiling mounted 205, but it may depend on the environment in which the AP is placed (objects may cause more RF attenuation, etc.). The 205H (and 303H) have "slightly directional" antenna patterns, but I doubt that it will have a noticeable impact. RF performance numbers (transmit power, receiver sensitivity) are very similar.
Note that you may want to consider the 303H instead of the 205H. The 205H has been announced to go end of sale (by 5/1/2018), and the 303H is a lower cost and more capable replacement.
Also, if you're sure to use it in a desk mount scenario, we have the AP-303HR bundles, where the 303H comes with a pre-assembled and attached desk stand, a power adapter and AC cord.
There are two versions of this bundle. AP-303HR-US comes with the AP-303H-US and a North-American cord, while AP-303HR-EU contains the AP-303H-RW and a european power cord.