Comparing burning methods (thus including burning speed) for a given media/burner combination, is one of the really legit uses of PIE/PIF scanning.
But why spoil media in making test discs? Just burn what you actually need to burn, and scan the disc.
If you don’t burn slower than @6X nor faster than @12X (assuming you use 16X rated discs), and you use good discs, you have about zero chances to get bad burns. Your burns will be entirely usable. If you don’t have enough data for the full burn, just add random data to fill the disc.
Want to make your life simple? The usual rule of thumb that many of us apply here, is to burn everything (8X rated and 16X rated discs) @8X for best results (assuming one’s burner is less than 2 years old). Though most of the time the difference between 8X and 12X burns is not very significant in terms of homemade PIE/PIF scans.
Important: Pioneer drives are notoriously untrustable and atypic scanners. Don’t scan with a Pioneer drive unless you really, really know what you’re doing, AND you have a very good grasp on ECMA specs, AND you have performed lots of in-depths comparisons of many scans performed in several different drives. Same goes for NEC drives.
The scanning trio: Benq, Lite-On (and rebadged), Plextor.