Although my basement is a little deeper than 7', I went through essentially the same argument with myself....drywall vs dropped ceiling. I went with drywall and am very glad I did. The trick is to build in a couple of access panels that can't be seen (easily), bul allow you into at least a couple of important intra-joist spaces, such as those that carry kitchen or bath plumbing pipes. I've had to cut into the ceiling twice in the last 5 years to retro fit a couple of items I had not ever considered in my basement finish planning. But if you cut the drywall right on the joist centers, then putting the square of drywall back is much, much easier.