Ahh this is THE question. When it comes to seedbanks and breeders I just asked myself who has been doing it the longest. The answer Dutch Passionm they are the leaders in stablizing strains IMO. As stated above there are many good breeders out there but it takes a certain amount of time(or generations of a certain strain) to get a strain to produce the desired results 90% of the time.
So if you go on say Paradise seeds and they are selling there version of Blueberry(I am just using this as an example DP owns the only true BB strain) it may have 10 years of stabilizaiton where as with Dutch Passion it has been almost 30 years.
Way back when, when seeds were first becoming available on the internet you had 1 choice really get a pack of 10 seeds plant them all and hope you get more females than males. Most of the old school growers only knew this way of growing, then something amazing happened! There was a revolution in the seeds that were being produced and for the first time when I went to buy a pack of beans I saw "Feminized" seeds, guess who pioneered that...... Dutch Passion. It took a long time before they would actually realse the seeds because there standards for breeding selection is second to none.
This is the same thing that has happened with autos. I have purposely waited almost 7 years to start growing auto's. The reason being is because when autos first came out(Lowryders) while yes they did autoflower, they were really small and not all that potent. It has taken this long to effectively breed all of the traits we love like yield and potency into the ruderalis genes that make a plant autoflower. Again Dutch Passion to the rescue, because many believe DP to have the largest collection of Landrace(old school original cannabis strains or "pure" strains" on the planet this allows them the best set of genes to start working with, thus creating IMO the best cannabis strains on earth be it photos,feminized, or autofem seeds.
I am currently growing DP's AutoXtreme and I picked that strain in part because I got the best of 2 world Dutch Passion and Dinafem(my 2nd favorite breeder) who did a 2 year collaboration to come up with the AutoXtreme.
Another thing that makes DP the best in my humboldt opinion is there germination succsess rate. I have been growing DP genetics for around 10 years or so and I can only remember out of literally hundreds of seeds only having 1 not pop(and I think it was my fault) I have never heard of anyone having trouble getting DP seeds to germinate.
The folks at DP have standards for breeding that would blow most peoples minds. Just take a look at the lineage and biography of how DJ Short made the Blueberry strain(thousands and thousands of plants were grown just to get "the ONE" that had the traits he was looking for)
If you choose Dutch Passion genetics you will not be disappointed, in fact lots of folks once they grow DP never grow anything else(I am a prime example)
Hope this helps, and thanks for the oppritunity to brag on my favorite Breeders on the planet! Sending Great Grow Karma your way friend! If you have any other questions about DP don't hesitate to ask or shoot me a pM