LOL, right...point is, I didn't need to buy weed and then fork over $100-150.00 for seeds. They came "free" with the weed. Now saying that, I have bought seed from seedbanks...White widow(the knock-off) AI, AK-47,Snow white, White rhino, Northern lights, Hash plant and grew them right beside bagseed and there wasn't a whole lot of difference. But hey, waste your money if it works for you.
I think this really depends on what you're comparing.
If you're pulling your bagseeds out of bags of premium stuff, they very well might be better than many commercial ceeds. If you happen to have a bag of kick-ass weed that you love, and it has ceeds in there, go for it.
But there are a few problems here, not the least of which is that it can be really tough to find viable ceeds in high-end commercial weed. Even if you do find such ceeds, you don't know what the plants will look like until you grow them, nor how long they take to finish (or even if they WILL finish). Bagseeds may be the result of hermie-pollination, and may have hermie-prone genetics, growing into hermie prone plants. . . .that's another risk. Bagseeds are usually "bastards" that may end up different than the plant in the bag they came out of.
Another problem in this comparison, is that a lot of the strains you mention (eg White Widow, White Rhino, Northern lights) are likely watered down versions of the famous originals. I've grown at least one version of so-called "White Widow" that was just terrible. . .no frost, no taste, no potency. I've grown
ceed out of schwagg that was actually quite a bit better that that in EVERY way (yield, flavor, and potency). I've also seen some pretty sad excuses for "Northern lights" too.
But of course, I've also
grown commercial strains that completely blow away the schwagg-ceed in terms of
flavor, potency, etc.
One big advantage of using actual commercial ceeds is just that you'll have a much better idea what to expect in terms of plant growth, yield, and flowering time than some random bagseed.