Looking only at the number of ETFs can be deceiving. Let's say that I hold a total US stock market index. This may be one ETF, but I still hold funds within all 9 Morningstar style boxes. You could break this into 9 different ETFs, (LCV, LCC, LCG, MCV, MCC, MCG, SCV, SCC, SCG), but that doesn't mean you are any better diversified. In fact, holding more underlying ETFs can create tax inefficiencies as indices reconstitute themselves (e.g., a SCG stock may grown to be a MCG stock. A total market index doesn't necessarily need to make any trades to reflect this change, but the SCG fund will need to sell the stock and the MCG fund will need to buy it).