No they don't look the same in the end.
The SKP (Slip 1 K1 Psso) has a leggier left slant, usually prescribe by the designer to give "a look" for a leaf or a leafy appearance.
The SSK just simply decreases a stitch with a minimal left slant. In which case I use the SSK "improved"...as shown on this website under basic techniques/decreasing.
On that plain ole swatch it doesn't seem to matter, but in reality, it matters.
I always use the style of decrease that the designer prescribes. "If it ain't broke, why fix it?" is my motto. She is the designer, I am the knitter. That is what I pay her for...her designs!