personally im always up the ladder a bit when i retreat, but i noticed some players can just dance around the ladder then climb never getting a false climb, i assume these are the guys using spring entry rather than landing spot?
Yea, I 'dance' sometimes...if I am going for max points. Dancing is something you can do to ensure you will pass a spring screen as fast as the game will allow. And yes, the sooner you can recognize that a spring is going to be long, the easier it is to do this 'dance'.
I've never measured in any way, but I believe all of the springs are exactly the same...as far as how high they bounce and everything. The only difference between springs are the points on the horizontal axis where they bounce.
Long springs 'look' like they bounce higher, but I don't believe this is the case. It's somewhat of an optical illusion based on observing how much higher a 'long' spring is vertically, when it enters the screen from the left...and also when it comes in contact with the ladder you must climb to finish the level.
The springs are essentially bouncing in a perfect parabolic series. All springs. Long springs are bad (arguably impossible) to finish the level on, due to the fact that the vertex of their bounces reach the highest up the ladder...giving them the best chance of hitting you.
The shortest springs are shifted left, as far as where their bounces come in contact with the floor (compared to long springs). They come out lower when they enter the screen, and are on the downslope in their parabolic bouncing pattern. Some think these shortest springs are the best springs to go on, but the first time you get a bad jump and get hit on the right foot by a short spring bouncing up at you...you'll realize the best springs to go on lie somewhere in-between.
I've called these springs the 'sweet spot' springs in other posts. As far as categorizing as long/short...they are somewhere between medium/short. The sweet spot springs give you the best chance to climb the ladder successfully becasue the vertex of their parabolic bounces are '1/2-the-width-of-the-parabola-itself' distance away from the centerpoint of the ladder...which means one of their bounces hits directly in the center of the ladder...essentially giving Jumpman the maximum amount of time to safely make his way up the ladder without being hit by the spring.
You can even have a bad jump, or have your hand slip off the controller for a fraction of a second...and still make it up the ladder safely if you go on a sweet spot spring.
In the end, it's easier to simply go on any and all short, medium, medium/short springs...after a long spring. You can make it up safely on any of these...and the faster you make it up...the more bonus left on the timer, which means more points.