The result is the same (decreasing one stitch) but is used in shaping raglans or in lace patterns as the directions of the stiches go in different ways. Passing 1 stitch over another is used for right hand side decreases and k2 tog for left hand decreases on raglans IYSWIM. In lace patterns the two different types of decrease move the stitches away from the lace hole.
If you are knitting stocking stitch in a very plain yarn then it will probably show up - especially on thicker yarns. Does it matter? Thats up to you!! On a semi solid, multicoloured or textured yarn then it probably won't be that noticeable,
I shall do the tension square to see what the difference is. I just can't seem to visualise it. For this current project the question is academic, in any case, as I've already finished the psso sleeve and am working on the K2tog sleeve, and anyway it's in angora. (Ghastly stuff to work with [teeth-gnashing, hair-pulling-out emoticon])
If you imagine that it would look like a skein of geese following one another if you did k1 psso on the right hand side up to the top of your sleeve but if you did k2tog on the right hand side it would look like a bomber flight headed in the direction of the seam edge.