2010 was a good year for many mutual fund managers, as the stock market jumped significantly for a second consecutive year. However, with increasing market returns comes increasing expectations for these money managers to reach and surpass their benchmarks.

One fund manager who hasn't had to worry about trailing his peers is Noah Blackstein, whose Dynamic U.S. Growth Fund returned more than 50% last year. That was enough to top the list of unlevered diversified stock funds.

Blackstein has been on my radar for a while because he doesn't follow traditional mutual fund mandates, much like Bruce Berkowitz of the strong-performing Fairholme Fund. Investors have started to catch on to the added value that this new wave of more active managers brings. In Berkowitz's case, it's why Fairholme had more than $4.1 billion in net inflows as of late December, more than any other domestic equity fund in 2010. It also helped that Berkowitz produced returns of more than 25% during the past year. Though these two fund managers may have different investing styles, it is the value they each add respectively that I believe sets them apart from the majority of their peers.

Similarity in differences
Blackstein's and Berkowitz's investing styles are very different. In fact, in looking at their portfolios, you won't see any of the same stocks. Overall, Berkowitz is a value investor, while Blackstein is looking for the best growth opportunities. However, both focus on large positions in ideas that they have a strong conviction in. Blackstein and Berkowitz keep the portfolios small and heavily concentrated -- each portfolio currently has within a few picks of 25 stocks each -- unlike traditional managers who prefer more diversification just to manage risk.

Most mutual fund managers have a mandate to fill out their portfolios with smaller positions in many stocks to make their funds more marketable to the average retail investor. Blackstein and Berkowitz don't believe in this type of window dressing, and it allows them to follow their own investment strategies more closely.

Overweight in a good way
For example, as of Sept. 30, close to 60% of Blackstein's portfolio was allocated to technology stocks, with Apple (Nasdaq: AAPL), NetApp (Nasdaq: NTAP), and VMware (NYSE: VMW) comprising about 20% of the total portfolio.

Blackstein said he is "a big believer in the move from traditional cell phones to smartphones, and Apple's iPhone is at the forefront of that." This proliferation of smartphones and mobile computing includes a significant need for more data storage, both hardware and cloud-based, which helps explain why his top three positions are heavily weighted to this area of technology.

Blackstein's fund actually has no exposure to the financial sector, which represents another large contrast to Berkowitz's Fairholme Fund. Berkowitz is even more heavily concentrated in financials than his counterpart is in tech, with nearly 74% of his assets allocated to the sector.

Blackstein steers clear of financials because as he says, "There's less likely to be a rip-roaring company in the financial service industry." Berkowitz might disagree, as his top financial stock AIG (NYSE: AIG) was up about 90% last year. Citigroup (NYSE: C) is another large Fairholme Fund position and increased more than 40% in 2010.

Bank of America (NYSE: BAC) and Goldman Sachs (NYSE: GS) have also earned heavy weightings in Berkowitz's portfolio. He believes these top financial picks have earnings power and balance sheets that are stronger than ever. In addition, he believes the pessimism regarding the industry has allowed him to pick up shares of these hated financial companies at significant discounts.

Adding value in 2011
Even with differing opinions in regards to stock picking, these managers' convictions are comforting and one of the reasons for their success.

Noah Blackstein and Bruce Berkowitz were big winners in 2010, but for all managers the slate is wiped clean in 2011, and a new game begins. While the year may be changing, I still believe investors should continue to seek out managers like Blackstein and Berkowitz who challenge the conventional mutual fund strategies and rely on their convictions and instincts to make concentrated investment decisions. All fund managers get paid to manage money; only some add value to it.

Andrew Bond owns no shares in the companies listed.  Apple is a Motley Fool Stock Advisor pick. VMware is a Motley Fool Rule Breakers choice. The Fool owns shares of Apple and Bank of America, and through a separate account from our Rising Star series, also has a short position in Bank of America. You can follow Andrew on Twitter @Bond0 or on his RSS feed. Try any of our Foolish newsletters today, free for 30 days. We Fools may not all hold the same opinions, but we all believe that considering a diverse range of insights makes us better investors. The Fool has a disclosure policy.