After what seems to be months and months of searching, we've settled on purchasing the York and Metro sofas, both in fabric. I've been able to look at about 4 York models in different furniture stores. None have had welting on upholstery. I've seen one Metro (in person) and one Metro (photos on this web site). The Metro models have both had welting at seams.
What are the pros and cons of having welts? Of not having welts?
Its just a matter of style and preference, both are there to add closure to two joined panels. There's not really one that's better than the other, any more than an apple is better than an orange. They're just different! I tend to go with welt trim on fabric pieces, but like double-stitching on leather, especially burnished leather pieces (I also like custom stitching, which costs a bit more but really changes the look on leather)
All Questions should be asked in the forum
When I am asked this question by my customers my usual response is that a welted box cushion is a more "formal" look as opposed to a non-welted roll-front cushion which gives the furniture more of a "casual" styling.