Both techniques are good.According to your business and budget you can choose these techniques for your promotions.If budget is low SEO is the best choice, If budget is high and need great growth in promotions you can use both techniques.
White hat technique is in which we follow the guidelines of google, where as in Black hat technique we don't follow the guidelines of google.Black hat technique uses cloaking,keyword stuffing,hidden links,hidden texts etc to get more traffic to our website.
Internal linking is where we can create links inside our websites, with the help of internal links we can reduce bounce rate.It will help to maintain average session time in our website.