Market Samurai SEO Competition Question

I must be missing something here, and I apologize if the answer is really obvious and I just missed it. When I run SEO competition on Market Samurai, lets say that it shows 500 backlinks for a certain website. When I run a backlink check on SEO Spyglass, however, that same website only comes up with about 20 backlinks, 18 of which are missing links. This isn't just one site either, I have checked multiple sites against both programs and many times the numbers are nowhere near the same. Why the huge difference in backlink numbers? I'm pretty sure my settings are equivalent between the two and I can't figure it out. I don't want to be passing up niche opportunities because I misunderstood/got the wrong information.

Market Samurai uses MajesticSEO to check backlinks by default and Seo Spyglass uses other services. Majestic SEO always shows more links than other's.

So should I be going more by what that says or what SEO Spyglass says? Thanks for the info.

go with majestic seo/ms