DMC Rebellion and DmC Rebellion are both good weapons in design, they reflect both Dantes. DMC Rebellion had the skull guard with a horned side and a un-horned side. It reflects Dante's duality; his demonic and human nature. Also, when the sword's guard opened up and the same thing happened in The Legend of Zelda: Wind Waker and then later in Skyward Sword, DMC Rebellion felt like DMC Dante's own Master Sword, but with skulls and we all know skulls are awesome.
DmC Rebellion feels ethereal; it's not part of the human world. DmC Dante being the angel/demon hybrid he is, really reinforces this. Almost everything about him is inhuman, except for his appearance of course. He just doesn't belong with human, or even angels and demons for that matter. The blade itself looks clean, but the hilt looks warped. DmC Dante looks normal, but most people do as well, what's inside of him is pretty messed up.
DMC Yamato (Ya-mot-toe) and DmC Yamato (Yea-mat-toe) just look like plain katanas, especially DmC's which was literally a plain katana. While DMC's Yamato is more elegant with the ribbon, white-wrapped hilt, dragon emblem on the pommel, and I think a trimmed sheath. But I think most of this has to do with the nature of katanas; you can't really make them look all that different. Maybe jagged edges, different wrapped hilt, different tsuba (guard) or no tsuba, designs on the blades, but it'll just end up as a katana. Straightening the blade, shortening or lengthening the blade changes it into a differently named, but similarly looking blade.
Theme-wise, they go great with both Vergils. DmC Vergil uses it almost like a cane, and as he states: "All war is fought with deception and you have been deceived." Yamato can, in supernatural cases common with books, films, anime, cartoons, games, etc., slash without being drawn fully, meters away from the wielder, and through dimensions, etc. The two Vergils don't have to work hard or even be next to you for you to be dead. By drawing slightly, the enemy will never know what hit him; deceived by his opponent. However, DMC Vergil appears to be honorable than DmC Vergil. Thinking on that, I think DmC Vergil should of had a shirasaya, a katana without a tsuba, and maybe a dagger inside of the sheath like Mugen from Samurai Champloo. It'd make DmC Vergil more deceptive, dishonorable, and a very true to his own words. Otherwise, they both are simple, effective, and dangerous blades, everything the two Vergils need. Afterall, they both have different styles compared to both Dantes.
Edit: How David de Latour pronounces Yamato, is that an accent thing?
