Is one more dominant than the other? Is one considered easier to learn than the other? Are they used in different circumstances? The accepted solution will answer these questions at a minimum.
In mainland China, simplified Chinese characters are the dominant form of written Chinese. It's the type of characters used in newspapers, most books, in subtitles on TV, in dictionaries, at school etcetera.
Traditional Chinese characters mainly used in Chinese-speaking communities and countries that were not under the governed by the Chinese Communist Party when simplified characters were introduced in the 1950s and 1960s, especially in the Republic of China ("Taiwan") and Hong Kong. (Singapore also introduced simplified Chinese characters.)
So if you want to read materials printed in the People's Republic of China ("mainland China"), you will need simplified Chinese characters. However, this does not mean that traditional Chinese characters are not used at all in the PRC; my Chinese language exchange partners have told me about learning traditional Chinese characters at school in order to read classical Chinese poetry. In addition, it is much easier to infer the simplified version of a traditional Chinese character than to infer the traditional version of a simplified character, even if you are aware of some of the simplification rules.
It is hard to say whether simplified Chinese characters are truly easier to learn than the traditional ones. One reason is that the simplification concerns only a small percentage of the Chinese writing system, even though it affects many frequently used characters. In addition, progress in literacy in mainland China is also influenced by advances in schooling generally, so the increased literacy cannot simply be attributed to the reform of the writing system. Some people have even argued that the traditional characters make it easier to infer their meaning (i.e. from similarity between their shape and what they represent) than their simplified counterparts. However, if you want to learn both variants, it is advisable to learn only one of them actively (e.g. the simplified ones) and the other form passively (e.g. the traditional ones). Writing characters by hand is affected by muscle memory, so learning both variants of the writing system actively is very challenging.
Conclusion: Due to the strong dominance of simplified Chinese characters in the PRC (and legal requirements in some circumstances), it makes more sense to learn simplified Chinese characters.