Beverly, aren't you more of a "casual" rider where you like to "enjoy the view" and speed ISN'T the issue? I can see where with trail type riding (slower speeds), the longer cranks might work better for you. The longer arms give a little better "torque" for accelerating from a stop or "crawl".
I stick to mostly flat pavement and ride a bike because I don't have a car. I pretty much want the fastest speed that I can comfortably maintain. I'm NOT fast, so going from 10 MPH to 11 MPH is a 10% increase! The shorter cranks HAVE helped my speed slightly, but they have REALLY helped my endurance. At this early time, it appears I can ride about 60-70% further with the same level of fatigue. On my shorter errands (1-2 miles), I can "crank it up" an extra 2-3 MPH. That doesn't help much when you speed up to a stop light, but maybe I'll catch a few when they are still green Actually, there is one "timed" light I can now catch with a little "burst"! If only it was on my "usual" route