Sinn U18vsLongines LONGINES SPIRIT FLYBACK PROTOTYPE

The Sinn U18 is praised for its unique deep blue/green dial with three-dimensional oxygen bubbles that change with light, and its comfortable, easily adjustable bracelet. Owners find the watch stunning and a piece of history, appreciating the refined hands. The Sinn U18 features a 44mm, 15.5mm thick case made from German submarine steel, offering a 2000-meter dive specification and Sinn's Ar-Dehumidifying technology, powered by a Sellita SW300-1 movement. The case thickness is apparent, and the watch comes as a complete set with box and papers for $3,000-$3,680. On balance, owners and reviewers rate the Sinn U18 highly for its striking dial and robust build.

Owners widely praise the Longines Spirit Flyback Prototype for its attractive finishing, COSC-certified movement, and value as a flyback chronograph. Reviewers highlight its refined 39.5mm case and simplified dial, while some owners appreciate the reduced thickness and improved wearability compared to larger variants, with a lug-to-lug distance noted as potentially long for smaller wrists. The watch features a 68-hour power reserve and a bespoke L791.4 movement. However, the case thickness is a consistent point of discussion, with multiple sources citing 17mm, though some reviewers suggest thoughtful design makes it wear closer to 13.5-14mm. Owners are split on the dial's aesthetic, with some preferring previous configurations with gold subdial rings and concentric textures over the current flat matte dial and cut-off numbers. The leather strap is also noted as stiff and pinching.