To build muscle tissue, you're body needs the 9 essential amino acids (EAA's). This has always been the case and is basic nutrition 101. What the term 'essential' means is that you're body CANNOT produce them by itself, meaning you have to consume these EAA's from a whole food source (chicken, beef, eggs etc.)
Of the 9 essential amino acids, 3 of them are referred to as branch chain amino acids or BCAA's. BCAA's ARE A TYPE OF EAA'S!! These 3 BCAA's are leucine, iso-leucine and valine and these are the amino acids found in a lot of intra workout / BCAA supplements.
A lot of the studies conducted on BCAA's, found that they can do a lot of really cool physiological things like prevent muscle breakdown during training, increase protein synthesis, increase muscle protein synthesis (amount of protein actually able to get into muscle tissue), reduce muscle soreness, among many other benefits.
So what does this all actually mean from a supplementation point of view? Neither is better than the other! It basically comes down to your nutrition and your specific needs!! If you're diet is on point, you're consistent with getting whole food sources in every day, thus you're feeding your body these 9 essential amino acids every day, than a BCAA supplement would be of particular use to you based on those cool benefits listed above that BCAA's have to offer.
Flip the script and if you're a vegan / vegetarian or even somebody who's just inconsistent in consuming your meals every day, getting these 9 essential amino acids in from whole food sources suddenly becomes more of a struggle and an issue. You don't have the luxury of feeding your body these EAA's from chicken, beef, eggs etc like everyone else thus must source them elsewhere. This is where an EAA supplement would come into play, making it a sh*t load easier to ensure your body is given these essential amino acids that directly contribute to building muscle tissue.
To make things easier, EAA's supplements would benefit those who are inconsistent with their nutrition and/or vegans and vegetarians where as BCAA's would help those who don't have an issue getting their 9 essential amino acids in from whole food sources.
There are a lot of companies nowadays who are actually formulating and combining the two into one product. They have their EAA breakdown but have also added a significant dose of BCAA's found in most BCAA supplements, giving you the best of both words! We imagine this is the route most companies will go down as time goes on as such a product literally caters for everyone.
We hope that helps in shedding some light and info on a debated topic making the rounds within the fitness world.