If you are storing indoors for winter, you want something of a soft, absorbent fabric that will tend to breath as well as possible. Water resistant is not even desirable if you winter the bike inside.
I have a Dowco dustcover, size extra large ($40)and it is too big but useable. Large is probably about the right size. The small does not even fit over a 600 very well. A queen sized fitted bed sheet might be just right to protect your busa from dust and perhaps cheaper. I find that even a loose fitting bed sheet hinders condensation from evaporating. There are merits to leaving the bike uncovered if the air temps change and you see sweat forming on the gas tank.
I did a great deal of thinking and got numerous recommendations before buying an outdoor cover. You must consider the reasons you are covering your bike. A Geeza would be my first choice for protection because they fit perfectly. Unfortunately, they look so cool and are so expensive, I feel that they encourage theft. Personally, I would be nervous leaving one of those on my bike in a parking lot even iif the cover was locked with a cable as Geeza shows in some of their promos. Geeza is a great company though and they make an outstanding product. Just not a good theft deterent IMHO.
For outdoor protection, I wanted something that would fit well and conceal the bike so I went with a Dowco Guardian Weatherall Plus Cover.
Dowco Guardian Weatherall Plus Cover - Street Bike - Motorcycle Superstore Order the sportbike model( all black); not the Black and Grey. The Sportbike size fits the busa snug but not too tight. It has a soft inside to prevent scuffing and the tail and windscreen portions have an extra soft liner. The elastic bottom can be positioned above the pipes if you have stockers. I have not had any trouble with the inside of the cover burning on pipes but My aftermarket muffler cools down within minutes. there is a D-ring and nylon strap that can be pulled under the bike and fastened to tighten down and prevent the cover from blowing away.
My only complaint is that this cover is very bulky. Not something I enjoy carrying with me on a daily basis------but I usually do if the bike is going to sit outside for more than 30 minutes.