Why are hydraulic roller lifters, different on different sides in the engines?

It seems I can only download "URL" pictures & I've got "JPG" so I reckon there'll be no pics from me.
But there's a thread here called "89 roller-cam LA 360 w/Magnum heads" (or such) by cuda888 here, showing pictures of the lifters showing the difference in the oil-holes.

The most important knowledge thou is why they're different springed & what it would mean to put the same on both sides, pictures or not...

& if it matters what direction the oil-holes points when you or me gonna put it all together again.