Burleys aren't as "sexy" Imho because of the niche/price point they targeted. Burley was more focused on making good, affordable tandems, than on high end tandems. (although they later added some high end offerings).
On a dollar to dollar basis, I think the Duet was as good or better value than anything offered by Santana, and I don't believe Co-Motion has evered offered a bike in the Duet's price range.
So a Duet isn't as good a bike as a Co-Motion, or a higher end Santana, but it's less expensive, and hits that sweet spot of being a serious bike, that's up to anything you could want it to do, and still relatively affordable.