to be realistic, no one is going to gain 10-15 lbs of muscle in one cycle so I would keep that in mind first. You can gain 15 lbs of weight, no problem but 3 months later, you will find most of it is gone. Primo will produce real muscle gains with much less water. I t will also give you a harder more defined look with the right diet. Deca will bloat you up a lot. If you just want mass, go with deca. If you want quality, go with primo. If you use the deca you will need to increase your test to at least 400mg to avoid sexual dysfunction. Even then, its still a possibility.