Most are good. But if you're asking such a question, then it's quite likely that you're not ready to use any of them, though I could be wrong (and I hope I am). Many people around here, seem to like GSA. It's not my first choice, but to each their own. It's got rave reviews.
Best? No there is no any best tool. It's all depends on your usage. Few renowned ones are 1. GSA Search Engine Ranker, Captcha Breaker and SEO Indexer 2. Money Robot 3. Scrapebox 4. Xrumer 5. FCS NEtworker (not a tool, but web based solution)
Well I started using RankerX in 3 last week and i will have to say they are very good. I believe you can get more than 300 get high PR SEO backlinks You can use their 7 days trial and add the owner on skype, he was extremely helpful to me.
