In reply to Andy Hobson: Perfect answer, it pretty much comes down to how you choose to climb it.
However, it is worth noting that personal style is always heavily influenced by what other climbers do and what is considered 'normal'. There are plenty of lines that used to be done as bold solos with nothing more than a square foot of carpet used to keep boots clean that are now done with 3+ mats and an army of spotters. This is reflected in that grades in some guides have changed from route grades to bouldering grades for many lines - NTBTA being a good example.
Therefore it makes sense that a line can have two grades and both can still be valid, although obviously you can't claim the route grade if you use a mat.