Yesterday I worked side by side with a collegue specialized in storage (SAN) and when he presented the disks to the Windows Operating System I mounted the drives and told Windows to start formating.
After a while my collegue asked me how far the formatting was and when I said X %, he told me I should have taken quick format to go quicker. Always willing to learn something I asked him what the actual difference is. The guy said that when you do a quick format, you actually don't do a format but the formatting will be done when you need the space. Quick format only defines the beginning and the end of the partition. Whereas the full format does a real format and goes through every sector on the partition. By doing this you will gain I/O performance my storage specialist said. This is interesting since one of the classic bottlenecks is the disk I/O.
So, OK it takes time to format 300GB but if I gain some I/O performance and in the best of cases I can do it at night while sleeping it is worth I think considering it.