QUEST l4 (30) keeps the L and U available to draw TRANQUIL on a future turn, scoring 60 points. In this case, the L and U are extremely valuable tiles.
MODE 9h (26) allows you to keep proper board dynamics by playing in the middle of the board while keeping a good leave and giving yourself a MODE-L hook next turn if you happen to draw well.
While it might be intuitive to play QUILT b6 and blocks the open U in the TW/TL alley, the best play is actually to use both of your Us and play UVULA j1 (24), creating a second lucrative lane for your U.