It is true what they say ''you will learn more by playing 3v3''.As everybody said in 3v3 you work with your team,you already know what strategy to choose,you plan your work,rush some countries,don't think about money (because allies can give you),etc. In 1v1 you will only learn how to play if you play against high experienced players such as me,etc. I played 1v1 4x more times than i did CW or 3v3.It is just what players like.I learned to play many countries in 1v1,such Ukraine vs Turkey,etc.I played against Acquiesce,Mou,all good players and that's how i learned 3k,5k,10k, and other countries.Be aware that 1v1 expansion won't work in 3v3,especially if those expansions are big and takes a lot of money,it is not worth.Since you know that Germany will take Poland against Ukraine (well usually),Turkey rush Russia south,so it is better to attack 1 country and take it then to split your troops and get 3 plus it could happen fails,critical,etc.And in 1v1 you have a big choice of strategies which makes you worry what to choose.
Also in 3v3 don't use expensive strategies because if you don't make good economy,you die even if your friends give you money.They may go bankrupt because of that action.Always before 3v3 start,work with your team like it is CW.You must take plans.If you play with no plans then you gonna fail.Like your friend take Paris and you also attacked it which was necessery.If you lose in 3v3 don't be mad,just think positive.Each time you lose you learn more.You learn that using that was bad,etc.And you try to be better every time. Playing 3v3 and 1v1 against low ranks won't give you anything... So in short version 1v1 and 3v3 isn't the same.It is whole different thing.