The best test value is the one that gets you the answers you are seeking. What are you looking for? If it is your direct male line then yDNA testing with FTDNA. Looking for breakthroughs in brick walls or wanting to find long lost cousins? Then autosomal DNA testing using companies like 23andMe or FTDNA's Family finder test.
Check the companies web sites and read about what it is they do. Some have free tutorials. Then choose the onewhich is the best fit for what you are looking for.
Don't go for "cheap" testing, because you get what you pay for, and it probably won't be enough information to get you to your answers.