So you haven't actually tried Adequan, or an injectable glucosamine?? So how can you say which results are better when comparing oral to injectable.
Also, when looking at the ingredients I am highly doubtful that the results you are experiencing with Aniflex have anything to do with the glucosamine, or HA in the product. First and foremost I notice the added Selenium and in Selenium deficient soils, addition of this mineral alone can improve health greatly. Next is the MSM and Creatine which are both effective at improving the strength of connective tissues, of which there are a lot near joints. The final thing I notice in the product is Yucca, which will show up in a drug test. It is not allowed for competition horses because of it's anti inflammatory effects and it is because of the inclusion of this ingredient that I believe the majority of the effects (which I'm guessing were rather immediate) are due to.
Even with Adequan injections, it takes a full month of 5ccs every 4 days before results are seen. Oral supplements, with the lower dose and how little is actually absorbed should take even longer than that to show results. Any immediate effects are usually due to anti-inflammatory properties of the supplement.
They say money doesn't buy happiness -- well happiness doesn't buy horses!