sure, seeds are always going to be hardier, usually stronger over all plants then clones. seeded plants are less likely to get diseases. pm, etc, etc then clones.. after awhile, clones will just be more succeptable to these things..
as to the second part, how do you make seeds from clones where there's only a mother plant that was ever created, and no dad of the same plant? sure, you could s1 them with some cs i guess, but not every strain will throw nanners when the use of chemicals are applied to them...
if you happen to know what the genetics of a strain are, like blue dream is blueberry x ssh, you can always find a nice ssh and a nice blueberry, and breed them together, but is that every really going to be exactly like the clone only blue dream where i'm sure a special pheno of each was used? well, i guess it depends on who is doing the breeding.. i've seen a lot of grows of hso's blue dream, and i'm not saying they're not nice plants, i'm just saying i've seen some very indica leaning phenos where as the clone only is nothing indica about it..very thin leaves, a nice stretch in flower, and about a 10 or 11 week flower time, depending on how you like your smoke.