I started out with bagseed. Some of the bud I harvested was better than my original schwag, some was worse, but I was also inexperienced. I cloned the same females over and over though and each grow got better. Then I ordered some seeds from nirvana (ak-48 and ppp) and was blown away. No comparison between these genetics and the bagseed I started with. The plants are healthier, grow fast and bigger, are hardier, yield more, and are more potent. Maybe it's the fact that I only had a small selection of random genetics from the bagseed, and it wasn't specifically bred to be grown indoors, so im not able to maximize the genetic potential, where as I can utilize the good genetics better.
If you know how to grow you should be able to get a final smoke that is better than the schwag you started with. I have heard of people hitting the genetic lottery with schwag seed, but really it's a crap shoot. It might be great genetics, it might not. But when you order good genetics you know you are getting good genetics. Considering the price of weed, if you are taking the trouble to grow I think it is absolutely worth an investment in good genetics. You can clone as many plants as you want after they are established. Bagseed is a great way to learn though. I learned a lot from my bagseed grows. Once I got decent at growing it was some pretty good smoke too, but not as good as my ak-48 or ppp.