Borealis Watch Co. Porto CovovsSinn U18

The Borealis Porto Covo is widely praised for its 39mm size and unique cantilevered indices that create a 3D effect and depth. Owners note the indices' floating appearance is a well-executed design. One owner reported poor accuracy and a terse customer service response, while another wished for a 42mm size option. The $395 price is considered reasonable for a microbrand, though some feel it does not compare favorably to AliExpress options. Overall, owners appreciate the Borealis Porto Covo for its distinctive dial design and wearable 39mm case size.

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.