Blackhat SEO is done by breaking the rules of SEO world. This technique will not follow the rules defined by the good SEO practice. You will get the higher search ranking, no doubt in that. But it just quick return, there are no long term results provided by this technique. It will target the search engine instead of human audience.
This technique uses the SEO strategies as keyword stuffing, link farming, hidden texts and links, and blog content spamming.
The main dis-advantage of this technique is that, your site can be banned by the search engine and will be deindexed.
Whitehat SEO technique will follow all the guidelines defined for the proper SEO. It will target the human audience instead of search engine.
This technique uses the SEO strategies as keywords, and keyword analysis, doing research, rewriting relevant meta tags, backlinking, link building and writing the contents for the human readers.
The result of this SEO technique is long term. So the main focus of this technique is writing the quality contents.
It's always recommended to go with the white hat SEO.