In Memento, Leonard doesn't lose his memory when he goes to sleep, he just can't form long term memories. This affects his whole day, Leonard can start a task or conversation and not remember starting it by the time he gets to the end.
There's a scene that starts with Leonard in a hotel room, sitting on a closed toilet, fully clothed, with a bottle of alcohol in his hands. He wonders why is he sitting there and if he's drunk. He then takes a shower. Because he doesn't know why he's in the hotel, he doesn't know why he's in the bathroom, etc. He literally forgot he broke into the room to ambush a guy as he was doing it.
Whereas in 50 First Dates, it is how you described. Lucy replays the same day, she resets when she sleeps. But during the day, she can recall what happens. She can tell you what she had for breakfast, where she got her pineapple, who she met, etc.