the rat endgame (d4 d6 c4 e5 dxe5) is actually extremely deceptive and a line into which i'd enter when playing to win as black. just take a look at your favourite database and see how badly white scores from that position, despite its innocent look and engine's 0.00!
it's hard to tell exactly what's wrong with white's position, though i think that it's something like it's hard to find constructive plans, while black's position is full of potential.
on the ruy lopez, i go with the open when i play e5 and it has definitely served me well.
Btw, by 'Closed Main Line', I mean this: