Both augments have moments where they’re better than the other.
Flying pig is better when you can take advantage of the distance of a longer long jump by wall jumping off multiple walls, or jumping a large height to make the long jump last longer. If you can wall jump twice in the direction you want after long jumping, this augment provides a significant boost to distance traveled. It is superior in quick bursts of travel regardless of whether there is a wall or not. It’s also generally better the faster the merc is, since the percentage increase is larger the faster the merc is at base speed.
Meanwhile, Springy is great for open areas with little to no walls to jump off of, since the delay until you can long jump again after long jumping is shortened. This is generally a stronger augment for getting to the frontlines faster, but it’s not as combat-effective as Flying Pig. A burst of speed is often more useful in escaping around a corner than a consistent increase of frequency in long jumping. It is generally better on slower mercs, who can benefit from the increase in travel time the most.
In a nutshell, the longer the distance you have to travel in a longer period of time, Springy is better. The longer the distance you have to travel in a shorter period of time, Flying Pig is better. Flying Pig is better in combat situations and narrow areas, Springy is better in open areas.