Mandarin would be easier to learn between the two. Mandarin have the pinyin to help you pronounce chinese/mandarin words.

from Wikipedia:
Pinyin, or more formally Hanyu Pinyin, is the most commonly used Romanization system for Standard Mandarin. Hanyu means the Chinese language, and pinyin means "phonetics", or more literally, "spelling sound" or "spelled sound". Developed by a government committee in the People's Republic of China (PRC), the system was initially approved by the Chinese government on February 11, 1958. The International Organization for Standardization adopted pinyin as the international standard in 1982,[3] and since then it has been adopted by many other organizations. Since January 1, 2009, it is also the official romanization system in Republic of China (ROC). It is used to teach Chinese schoolchildren and foreign learners the standard pronunciation of Mandarin Chinese, to spell Chinese names in foreign publications and to enter Chinese characters (hanzi) on computers.
Sa Fookien, you have to memorize the pronounciation of each word

In the end, whichever dialect you choose to master, if you don't speak it often, makakalimutan mo rin yan.