Both tools suck, but MNF is far worse
MNF is based on the assumption that the more number of competing sites there are, the harder the keyword is to rank for, which is blatantly false. That's like saying "i have a better chance of winning a race with only 10 people in it when the fastest runner can run a 15 minute 5K than a race with 1,000 people where the fastest time is 30 minutes". If you want to win a race, the only number you care about is the fastest time you need to beat, not the number of competing racers. Same goes for keyword research. The only thing that matters is how tough the #1 spot is to beat, not how many are competing
Just search for "dog mistletoe party" and you'll see that it has an enormous amount of competing pages, yet none of those pages are optimized for the term and none have any of the backlinks using that anchor text. So overall, DONT buy MNF, it's terrible
As for Market Samurai, it's better than MNF, but it is slower, more resource intensive, and has less features than Traffic Travis, and Traffic Travis is FREE. If you bought Market Samurai, I highly recommend you get a refund and switch over to Traffic Travis, it is so much faster than MS and has on-page analysis stuff that MS doesn't have
Overall, the two best tools for keyword research are Traffic Travis and SEO Spyglass. Use Traffic Travis to get a basic glimpse of the top ten keywords, check on-page optimization, and track rank over time, and use SEO Spyglass to check how many backlinks are nofollow, how high PR the domains and the pages are that the backlinks are on, and what percent of the backlinks use the keyword as anchor text