There is actually quite a difference between the two recommendations; the second recommendation includes the first and a whole lot more.
Doctor #1 -
Medial sliding calcaneal osteotomy -
This is a basic heel bone osteotomy. They cut the back of the heel bone, slide the cut part medially (toward the center of the body), and attach it.
Doctor #2 -
Anterior calcaneal osteotomy (aka Evans osteotomy/lateral column lengthening) & Posterior calcaneal osteotomy -
This is a double calcaneal osteotomy.
There is the initial cut of the back of the heel, sliding it medially, followed by cutting the front of the heel bone and inserting a wedge (often from the hip).
Medial cuneiform osteotomy -
This is also known as a Cotton osteotomy.
It involves cutting the medial cuneiform (on the inside of your foot, there's your big toe, then a long bone (1st metatarsal), right after this is the medial cuneiform) and inserting a wedge (often from the hip).
That however is my non-doctor, just someone who does a lot of reading (and thus could be wrong!), answer..