Loose cushions give you the option of turning the pillows as needed, while attached backs won't need fluffing or rearranging. Be sure to sit in the sofa you are considering. Is it comfortable?
I now have a better quality sofa with the fabric I want, a great warranty (all hardwood frame has a lifetime warranty, pillows have warranty against breaking down for 8 years and all the fabric ...
It turned a dull gray over the years. As there were no slip covers, we would have to wash the sofa with an upholstery cleaner or to leave it be. On the hindsight, sofa sets with removable slip ...