In Last place... Mid-Block Crossing, there's just too much traffic trying to turn left at Greenway to make one work.
In 2nd/3rd... The Bridges (Ramp slightly leading over the Spiral). Major concerns, cyclists bypassing it and "wild cat" crossing mid-block. Speed of cyclists and skateboards on the descent, and difficulties for wheelchairists going up a 300+ foot ramp (even with landings).
Which makes the Underpass the clear winner. No waiting for signal changes, no long climbs or fast descents, and the raised level of the road would probably prevent cyclists from even wanting to try to "wild cat" cross. Good engineering should keep it out of the water during most high water events, and free of mud.
I've been having problems with the camera pop up lately... sorry about the poor selection of shots and quality (no flash)