I don't think I could say which is better. If you want Fems, you buy "S" seeds. If you buy regular seeds, you are buying the "F" version. The quality would be dependent on the work the breeder put into stabilizing the strain with the highest quality plants.
If you have limited space for plants or can only grow one plant, then I think feminized seeds should be what you choose. Also there are growers out there who are caregivers, they generally only want to grow female plants and they generally only want feminized seeds.
Anyone that wants to do any breeding/pollen chucking, well they will likely prefer F versions, (AKA regulars).