( SHLD) Vanguard and WisdomTree are the destination for buy-and-hold investors, while Direxion captured the traders. Meanwhile, Van Eck's Market Vectors ETFs were among the fastest growing ETFs last month.The fastest-growing ETPs, measured by growth in assets under management, were a mix of the most volatile emerging markets, leveraged ETFs and commodity ETNs. Risk was the trade of the month, and investors headed for these funds even if they lost money -- in four cases, all bear market funds, net inflows exceeded total asset growth. Many of these funds were also among those seeing the fastest growth via inflows, a topic I covered last week. The ones seeing the most growth due to price appreciation were Market Vectors Indonesia ( IDX), Market Vectors Brazil Small Cap ( BRF), SDPR S&P International Technology ( IPK), iPath Nickel ETN ( JJN), iShares MSCI Peru ( EPU) and Claymore/AlphaShares China Small Cap ( HAO). As long as the market advances, these more volatile funds will attract more assets and outperform the market. Among ETFs with more than $500 million in assets, those with the largest growth in AUM included iShares DJ U.S. Basic Materials ( IYM), iShares DJ U.S. Real Estate ( IYR), SPDR S&P Homebuilders ( XHB), PowerShares VRDO Tax Free Weekly ( PVI), iPath India ETN ( INP) and iShares Hong Kong ( EWH). The standout fund here is PVI. PVI holds variable rate demand obligations (VRDOs), bonds that usually trade with minimum denominations of $100,000, meaning most investors are unfamiliar with them. One selling point that no doubt attracts income investors is the stability of PVI. Its NAV has moved only 0.5% from its all-time high to its all-time low -- in nearly two years of trading. This means an investor's principle is protected while he or she collects monthly dividends, which currently amount to about 1.3% on an annualized basis. However, the variable rates adjust weekly, so this fund's yield will increase if rates move higher.