The styles of locking and popping both came to attention in the 70’s (locking has been around since the late 60’s but only really flourished in the 70’s). Both are often danced to funk music.
That’s about where the similarities in the dance styles end though. Popping and locking are based on completely different techniques and movement styles.
If you look at the vocabulary of moves that a popper would learn and that a locker would learn, you will see vastly different moves. Put the moves of popping together and there is a theme that unites them, and the same is true of locking also.
As for the difficulty level of each, this is harder to adjudge. If you have the basic locking technique down or the basic popping technique down, there is no reason why with practice that you can’t become a good dancer in that style. It is certainly achievable.
Which one is more difficult is largely down to you. Most people do one or the other, some people actually routinely engage in both forms of art. If you can’t pop, you will probably struggle with the dance style. If you can’t lock or relax your body when you move, you will find that locking will be difficult for you.
To give a general guideline, locking is a style of dance that is very difficult to learn on your own. It is not simple to learn popping on your own either but people have done it in the past because once you know how to do the basic pop you can teach yourself much that you need to know.
Most people find that locking takes longer to get into and to really understand compared to popping. To do either style to a high standard like the best poppers and lockers in the world do takes massive skill and it is not easier to become the best in one or the other.
One thing that may considerably affect the success you have in either dance style is whether you have access to a good teacher. Normally this will be a huge help and pretty much all the best poppers and locker have learnt how to do it from a teacher.
If you don’t have access to a teacher then you will discover that it is much harder to learn regardless of how much talent you may have. It’s possible, but will be hard work.
If you equate hard work to difficulty then the style you find easier will become dependent upon whether you have a good dance teacher within reach.
So the best thing to do is to find out for yourself which one you find easier. If you’re interested in one particular style and not so much the other, then you should follow your interest.
However if you’re interested in both styles but want to focus on one then spend a number of lessons learning both styles and you will quickly find out which one you have the better hang of.