UGG boots question<3?

okay so im a size 5 in women's uggs but i want to order the Big Kids uggs because they are cheaper. can anyone tell me what the major difference is between them, like do they look funny, do they lack in quality?...lastly, what size in Big Kids would i be if im a 5 in women? i know they say it's 2 sizes smaller but wouldnt a 3 be too small? please help me!