Miliband's monetary advantage is eyecatching in itself. But it also lets him trigger one of his electoral ploys. Smartly, if cynically, he has pledged to contribute one-third of his donations to a "fighting fund to help Labour win seats back at the next election". So the more cash he has in the coffers, the more he can hand over to Labour.
In practice, as he reveals on his site, this means he he has trained "180 Labour Party members in community organising to help the Party campaign on the ground." A barefaced tug on Labour heartstrings, sure. But, in a contest where none of the candidates has a clear political vision for the party, it's the kind of gesture which could make a difference.