The different strain between the 2 products is Threelac's Genus Enterococcus Faecalis and Symbion's Enterococcus Faecium.
I'm a research biologist from Vancouver, Canada and have done a lot of research on Genus Enterococcus Faecalis as I saw it as the workhorse of the Threelac I took some years ago to clean up my Candida symptoms.
This is really an amazing probiotic strain. Amazing because it comes from a pathogenic family which makes people really sick. Amazing moreso because the Japanese have gone deep into this strain to find a substrain that has all the potency inherent in this family but not the dangerous pathology.
I see many probiotics like Symbion with Enterococcus Faecium in them. It's not the same family though it sounds like it might be. It's a rather ordinary bacteria.
I've only seen Threelac's Genus Enterococcus Faecalis in one other product, also from Japan where it seems there is a certain knowledge about this strain. This company, Dr. Ohhira's probiotics uses their own substrain of this genus but it's delivered in a different form (not powder) and doesn't have the same punch against yeast that Threelac has.
BTW, Bacillus subtilis is also fairly common in probiotics.
I have seen other products compare themselves to Threelac saying it's the same thing for less but the manufacturer had either not had the knowledge or the courage to go into Threelac's workhorse strain and make it a part of their package.
Just my 2 cents as I have some inside knowledge of this world.