A decision in which neither choice is clearly favorable or unfavorable, or for which the outcome does not matter
It's really a toss-up between the red skirt with blue stripes and the blue skirt with red stripes. They both look good and fit well.
If you say that it is a toss-up whether one thing will happen or another thing will happen, you mean that either result seems equally likely. It's a toss-up whether oil prices will go up or down over the days ahead