Dollar cost averaging means that you are buying less units of the investment as it goes up so you are basically losing out on some of the gain compared to the lump sum purchase. (abcsofinvesting.net)
A lump sum purchase would be better because then all the money is invested in the market right away and can get the full benefit of the rising prices. (abcsofinvesting.net)
Some investors will save up their contributions and then make a larger purchase when they feel the timing is right — this is called a lump sum purchase. (abcsofinvesting.net)