Backlink watch only displays 1000 results, so if a website had 50K backlinks, it's not giving you an accurate picture of where the site is getting links. Having >100 backlinks from one site is better than 1 backlink from that site. Also, having 100 backlinks from different sites is better than having 100 backlinks from the same site. Noone knows exactly how much 300 backlinks from the same site will help and its effectiveness on SERPs. Just try to get a mixture of everything, like having your signature in this forum is giving you 146 backlinks at the moment, now you have got some links from the same site, try looking for other sites to get single links.
However, don't get bogged down worrying about questions like you have asked, I use backlink watch and go through the list and try to get the same links that they have (although usually only about 10% are possible). My advice is if you want to outrank this person, make a site that has better quality content and publish more quantity than them. Remember that backlinks are not the only factor for SERPs. Focus on what you can control (i.e. onsite SEO) by having META keywords/description, h1, h2, h3 etc, strong tags, underline, title, file names etc. For more about SERP factors I highly recomend taking a look at this blog post: 50 Search Engine Ranking Factors | Earn Money Online.