(Reuters) - Goldman Sachs said fundraising across alternative asset classes, particularly credit and real estate, remains robust in a low-rate, low-risk world, and sees more value in the stocks of asset managers that have a diverse mix.

The brokerage said although the outlook for traditional private equity fundraising remains mixed; real estate, distressed debt and mezzanine fundraising has grown steadily since the financial crisis, with a total funding pipeline of $225 billion across all three categories.

Goldman raised its ratings on Blackstone Group LP and Apollo Global Management LLC to "buy" and kept its top rating on Och Ziff Capital Management Group LLC given their significant exposure to alternative asset classes.

It sees opportunities in Blackstone due to its dominant real estate and fund-of-fund businesses and its relatively less reliance on IPO exit for generating performance fees.

The brokerage said Apollo's attractive 6 percent yield is diversified and relatively reliable with a high component of carry from interest and dividend income.

However, Goldman downgraded BlackRock Inc by a notch to "neutral" on valuation.

(Reporting by Satyanarayan Iyer in Bangalore; Editing by Supriya Kurane)