Here is a start
I assume if you like buying off the web that you have heard of and trust Newegg.
The difference between DVD-R and DVD+R is in the underlying method in which the blanks are made, read, and recorded to. DVD-R blanks use LPP (land pre pits) to record information such as sector address, laser power required by the burner, etc... DVD+R blanks use a phase change in the deflection signal to record the same information on the blanks. It appears that DVD-R is more difficult to record to at faster speeds than is DVD+R (not sure why). But, 16X record speeds is likely to be the limit for either of these formats since beyond this speed would require spinning the disc faster than it can handle.