I often find myself working on two songs that are virtually mirror images of each other. One will be a 2-5-1 with a sharp five and sharp 11, the other a 2-5-1 with a similar movement, but the 5 chord will have a 13 and flat 9 instead. When I first began to write music I was worried about my songs sounding the same, since I used the same ideas (the only ones I had at the time!). Now I realize that working like this makes a lot of sense and is an efficient way for me to develop ideas. I had three or four songs that all contained F maj 7 going to an F min / maj 7. Now, all my songs could still sound similar to one another in the larger sense, simply because I am working with the ideas that I have for some fairly standard progressions. I am writing what I can hear and nothing more.