In my experience both companies provide a high quality product with respectable resistance to scratches and damage. I find the defining factor that sways most clients one way or another are the aesthetics of the sinks or the styles they like. In general, I've found Blanco has a much wider range of styles, colours, and layouts which usually means I can find the product that suits most of my client's needs in one book.

In terms of performance of each brand, both are relatively easy to maintain, although with any granite sink its worth noting that the lighter the colour, the more likely you'll be to see staining or buildup from coffee / tea residue (provided you're an avid consumer of both). There are products on the market that take care of that easily (such as Bar Keepers Friend - or similar products).

There are subtle differences across the two brands, in specific I believe Franke has a coating on their sinks that helps with germs between cleanings. There a different drain appearances on each brand as well.

All in all the believe the defining factor for most people is finding the sink that suits their style and taste best, so my suggestion would be to browse each companies catalogues to see what stands out to you.

We have a Blanco double sink (one side full, other 3/4) in their deep brown (can't remember the exact name) and we love it. Put in 6 years ago and no issues. Never heard of the other brand.

No other composite sinks come close to the quality of the Elkay Quartz Luxe line. Order the samples and compare for yourself please.

I would not want you to get a sink you don‘t want, like stainless steel (that I chose), but be aware that composite sinks can crack. If you are going to get one anyway, consider one that can be flush mounted (like the Blanco Vintera) so that if you ever need to replace it you can do so with minimal distress.