One last thing to persuade you *not* to use the buck-boost configuration: If the LEDs go open circuit at all, even for a fraction of a second, that inductor is going to spike to some extremely high voltage and smoke the entire circuit very fast.
If this is your first switching regulator, go ahead and try this at a nice low voltage rating first - put it on 12V DC, and watch what happens to that circuit. I'd put bets on it reaching well over 100V at the low input voltage, and sparks developing shortly before becoming a smoke generator if you plug it into the outlet.
Just have two strings in parallel with some matching resistors. Better yet, hook up two mosfets at the ground level of the LED strings in a current mirror configuration.