When I go to G and check my bl's I enter 'link:www.yourdomain.com' and you will get your results. When you enter the same query with a space before the 'www' eg. 'link: www.yourdomain.com' the results are so different? Does anyone know why?
www and non-www are considered two different domains. This explains why results are different. Some backlinks are pointing to www and others to non-www.
Yes adding a space makes quite a difference hence why you will get different results returned in this scenario
Google isn't really helpful for finding backlinks by using the "link" search param. The best way is to search like this: "yourdomain.com" -site:yourdomain.com Google will return all sites where your domain name appears. Try it out! If your domain is a unique brand, just use "yourdomain" instead of "yourdomain.com". I hope you find this helpful
Worth implementing this: http://www.stepforth.com/resources/web-marketing-knowledgebase/non-www-redirect/#.VDZe4WcWbs0
Why would you add a space? The results are probably going to be different because you're not doing it correctly. Aside from that, I would use ahrefs to check my backlinks before Google. Google rarely updates to the point you can see, most of their backlink updating is done behind the scenes are you won't notice it for quite some time!
Ahrefs provides limited backlinks only and you need to avail their premium account to be able to access the full privilege. I would suggest you must try backlinkwatch it will show you more than what your other tools can provide.
Also you can try not bad russian instrument to chec backlinks: https://www.linkpad.ru/ sometimes it works better than ahrefs
If you don't edit on your google webmaster tools that you are the owner of both www.example.com and example.com, then Google will treat them as two completely different sites.