Is there much energy savings in just changing the tubes in a fluorescent fixture to LED? Unlike the fixtures that are straight line voltage (120-277) LED, the ballast is still functioning in the old fixture.
Percentage-wise, yes, LED bulbs use about 30 to 40% of their fluorescent counterparts for the same output.
How long this will take to pay back is going to depend on how often those lights are on.
If the labor cost to install the bulbs is high, there is more incentive to bypass the ballast so you don't have to go back up there and change it or bypass it later when it fails before the bulbs do.
in a newer office building with 8-foot ceilings, the lights are on maybe 10 hours a day, the existing ballast are likely original to the fixtures and fairly new, and you can work after office hours, drop-in replacements are a good choice.
In a 24-hour supermarket, where the lights are much higher, and replacing single ballasts here and there would be a monumental pain in the butt after the fact, I would go ahead and rewire all of the existing lights to bypass the ballast.
Recently I calculated the time for 100% ROI for replacing 400W MH parking light lamps with a 120W ballast bypass corn cob style LED. It was right at 2 years.
A single LED replacement in a electrical room or other seldomly occupied place may never pay for itself over a fluorescent tube.
In real estate they say location location location.
Choosing an ideal LED replacement is all about application.