While disk storage does play a factor in deciding which webhosting site to go with -- the overall factor should be the amount of bandwidth you're given per month (if any) -- especially if it's involving a business with web-related information.

1.5GiB of disk space is a good size to start with if you're only talking about webspace/webstorage but look for a webhosting site that gives you at least 10-20x that amount for bandwidth, meaning that you can push a total of 10-30GiB of data.