The difference is in the supplement facts. The 1:1 has 1500mg L-Citrulline to 1500mg DL-Malate while the 2:1 has 2000mg L-Citrulline to 1000mg DL-Malate. The difference:
You take 1tsp Scanted (A little less than teaspoon) 2x/day with the 1:1. This gives you the 1500mg:1500mg.
You take 1tsp Full 2x/day with the 2:1 for 2000mg:1000mg.
The 2:1 gives you more L-Citrulline while the 1:1 gives you 500mg less. How much difference is hard to say. If you was to take a full tsp of the 1:1 you probably will be getting around 1700mg or more I'm guessing.
Honestly, it doesn't seem like you are doing any better getting the 2:1 ratio because you will be using more powder and only getting a few hundred more mg of L-Citrulline. I am taking the recommended dosage of 1tsp scanted 2x/day and it seems to be starting to work. I began taking it around 3 days ago when I got my order. Taking it this way gives me 3000mg:3000mg per day or 6000mg between the L-Citrulline and the DL-Malate. I do like having the extra DL-Malate as it is a great energy enhancement that I noticed the first day I took the powder.
IMO the 1:1 is the best bet as you get an equal amount of each. If you take it 2x/day as suggested, then you will see results starting within about 3 days. I will update this with any difference I notice over the next couple weeks. I am going to take it as suggested for 2 weeks and see if there is any improvement and if not, I will probably up the dosage a litte. Maybe go to a full tsp or possibly 3x/day. The thing is you can take extra and it will not harm you, only give you more energy and extra blood flow. One plus is it seems as if I am hanging a bit fuller down under.
Side Note: Add Bioperine and Raw Maca to the mix. Bioperine will help the body to absorb the nutrients you are taking and Maca, well it provides fuel to the endocrine system which will aide in regulating your metabolism, energy, growth, and sexual development. Maca has also been shown to increase male libido and to increase sperm levels.
John