As far as bacteria in a bottle, up until Bio-Spira came out nearly 10 years ago, the other products simply did not work... mostly because they did not have the correct bacteria strains in them... and because of patents held by Dr. Tim and Marineland, these other products can't duplicate what Dr. Tim has done and continues to do.
Now, here's my layman's explanation of the history of Bio-Spira but you can read more on
http://www.DrTimsAquatics.com on his peer-reviewed studies, many of which are available on his websites.
Dr. Tim Hovenac, while the Chief Science Officer for Marineland (and having his PhD based on Nitrifying Bacteria) using DNA and advanced scientific methods, developed and grew the proper strains of bacteria (nitrosomonas, nitrospira and nitrosospira strains) for both FW and SW in the Marineland laboratory. Bio-Spira had to be kept refrigerated to put the bacteria into a type of hibernative state and only had about a 6 month shelf life. The patent(s) lasts for 10 years and will be expiring soon.
Since so many LFS and pet stores resisted setting up a refrigerator to carry Bio-Spira, it was mostly sold online and with a select few retailers. Dr. Tim and Marineland continued experimenting until he developed a way of putting the strains into a hibernative state without the need for refrigeration... the same way that N-bacteria live and can fly around in Nature until they find a water supply to call home... just like they eventually find our tanks when we are cycling a tank.
Now that he invented this process while still at Marineland, it was a joint patent(s) so when Spectrum Brands bought out Marineland and Dr. Tim went his own way and actually bought the original Marineland Laboratory building for his own building, he and Spectrum Brands both came out with their own products... that no longer needed refrigeration and have a 6-12 month shelf life. Spectrum also bought out Tetra so they released Bio-Spira as their SW product and for FW, they called it Tetra SafeStart. Dr. Tim released his product as Dr. Tim's One And Only and he has FW, SW and I think Brackish Water versions available through his website
http://www.DrTimsAquatics.com and also through a network of LFS and pet stores and online sources with one being
http://www.DrsFosterSmith.com.
I've read the published papers before but it's been a while so I'm not using any of the BIG words in the scientific peer reviewed studies but everyone is welcome to read them and know more about how Dr. Tim's One And Only works and does in fact have the proper strains of bacteria living in the bottle on the shelf. Dr. Tim's One And Only even comes with a vial of plain ammonia so you can add the product to your tank, dose it with ammonia and then do your testing to see that it works. If for some reason, the product you buy at retail or online was exposed to extreme heat or cold during the distribution process, this ammonia dosing and testing will also reveal if it didn't work and a quick call or email to Dr. Tim will get you a replacement package sent out via overnight mail so you'll have a fully working bottle the next day.
He's a member of several different fish keeping forums and I've communicated with him in forums and via email and I've seen him post in forums and back up his products and have seen the follow-up posts of people saying they received their replacement product, when it didn't work due to exposure reasons, and the replacement product worked as advertosed amd instantly cycles a tank for a full bioload of fish... not an overload, just a normal bioload.