I have found that a lot of cheaper brushless esc's have lower voltage cutoffs than I am uncomfortable with and this could cause damage to your new lipo .
They also allow you to use your lipo's with esc's that do not have a low voltage cutoff such as most brushed models .
They come in many varieties and from many sources .I find my self not recommending many of the high dollar brands due to them being the same as the low dollar units found on Ebay , hobby king , and others.
So spend a little money and you may save a lot more money .