My choice of what pattern to use is most often determined by the fabric on hand (or just spotted as being the most gorgeous I've ever seen...LOL).
Now the determination of which quilt to do next is a bit more difficult unless there is a specific event (such as the upcoming birth) that demands a particular one fit itself into the overall scheme of things.
Usually I'm working on several in various stages of completion at any given time. At the moment I think I have either 5 or 6 going...some have been on the back burner for a couple of years...and I had started a pink one recently specifically for a particular birthday present and then discovered the intended recipient had a different preference of color/theme, now that one is temporarily sidelined in favor of the new color scheme...but the pink one will instead go as a baby gift a couple of months down the line.
I specifically have chosen up to this point to stick to squares and rectangles because I'm comfortable with them, but the next quilt I intend to start, which is to be a learning experience for both me and a certain 11 year old will add triangles to the mix. She designed the quilt in Quilt Wizard then picked out the fabrics from my stash...hope I have enough, as all were ones I got on sale 2 - 3 years ago.
If not we'll figure it out as we go...
So how does this help you with your decision...probably not much!