Since there are a lot of languages under the Chinese language, therefore, you actually you also have a lot of choices when choosing a chinese dictionary and that is when the battle comes in. Now the Chinese languages are actually mostly composed of Mandarin, Cantonese, Taiwanese, Hunanese or Xiang, Hakka, and Shanghainese which also most of them you might not have heard that that particular language exists. So when choosing a Chinese dictionary, there are factors that you actually need to consider, like what is your purpose in learning the language, which place are you planning to use it since Chinese languages would depend on which part of china or country that have most people are speaking, like their main spoken language.
Now two of the most common available Chinese dictionaries worldwide are the mandarin and Cantonese Chinese dictionaries which mostly if you will ask a person who knows the Chinese language or who went to a Chinese school then most probably they will tell you to get the mandarin Chinese dictionary. However, always keep in mind that in choosing which Chinese dictionary, it would always depend on your purpose why you would need to buy it and why do you need to learn the language since there are still other factors that you need to consider in choosing which is which, like which would be very beneficial to you personally and career wise. And also, in choosing a Chinese dictionary, not only you would need to consider the language but as well the words that are on it, like if most of it has separate words that are translated in Chinese or it contains mostly basic conversational phrases that you can use anytime and anywhere.
Other dialects under the Chinese language are the Hakka and Shanghainese though it is actually kind of rare that you will be able to see a Chinese dictionary in either of the mentioned Chinese dialects. Also just like deciding whether mandarin or Cantonese Chinese dictionary that you will get, it would still be the same, it would still depend on whatever purpose you have in mind. Now if you want to get the Hakka Chinese dictionary or also even the Shanghainese Chinese dictionary keep in mind that most likely you will be able to use it in a specific or concentrated area in Asia or rarely all around the world, since the Shanghainese language, for example, is under the Chinese language classification of Wu which is spoken by only 6.5 percent of the people in the whole world.
Now if you are still confused which Chinese dictionary to get, then again you should first determine what is your main goal or main purpose why you wanted to learn the language. However if your main purpose is just to have Chinese phrases handy then most probably, you need to get the Mandarin Chinese dictionary since it is the most common and widely spoken Chinese language not just in Asia but in the whole world.