We have platform beds in all of our guest rooms and they are very comfortable. Guests often compliment us on how well they sleep. We ordered them online (Wayfair, I think). We have replaced all mattresses in both of our homes (7 bedrooms total) with 10" Tuft and Needle mattresses, which are shipped to the house. It's the mattress that makes the difference, I find. Whether it's on a box spring or platform doesn't seem to matter. Platform beds are less expensive and eliminate the need to buy a box spring.
If you decide to buy a platform, pay attention to the clearance under the bed and the height of the mattress, so you know how high the top of the mattress will be. If we ever replace our bedroom set, I suspect we'll buy a platform bed for ourselves too.