Sullenberger’s glider experience had no correlation.
US 1549 was not deadstick, and even if it was, the only thing it shares with a glider is having wings.
1549 had 35% thrust on the left engine, and 10% on the right.
The following was written by a glider pilot trainer, who openly credited the (then unknown) pilot with landing safely:
"Unpowered landings are also a crucial part of glider training--after keeping the nose down for much of the approach, the pilot must pull off what amounts to a full-stall landing, reducing speed until the wings are no longer producing lift, and bringing the nose back up. The result is an extremely low-speed, low-impact landing. To Hustead, that matches descriptions of Sullenberger's Hudson River landing. "That's a glider's instinct. It's the most perfect landing on water I've ever heard of," Hustead says.
If Sullenberger's gliding experience turns out to have helped to save lives, it wouldn't be the first time. In 1983, Air Canada Flight 143 ran out of fuel 41,000 ft over Ontario with 61 passengers onboard (the culprit was an embarrassing mix of human error and faulty fuel gauges). Capt. Robert Pearson, a certified glider, was able to safely land the Boeing 767 at a small airport in Manitoba. "I always say that glider pilots are the safest pilots. When the engine goes out, you're ready for it," says Hustead. "I would also hazard a guess that it's a good reason for power pilots to get their certification. They can come down here--I'll take them up any time."
--Erik Sofge
My Dad flew PBYs during the war, and won many "best-landing" trophies after the war. The PBY was best landed with the power chopped, and allowed to drop-stall onto ocean swells.