Here is a quick look at the effect the /i /x /y switches will have on your graphic images.

Starting image. Each square is 60x60 pixels. The total image is 180x180 pixels. |

/i This image has been sliced using the /i switch only. Notice only the middle edges have been prepared for the two pixel overlap. Each texture is now 64x64 pixels. The outer edges have been stretched but not overlapped. |
/x This image has been sliced using only the /x switch. The outer edges along the left and right sides have the two pixel overlap. Again, each texture is 64x64. The inner and remaining outer edges have been stretched but not overlapped. |
/y This has been sliced with the /y switch. The top and bottom edges have been prepared. Textures are 64x64. Like above, the inner and remaining edges have been stretched, not overlapped. |
/ixy This image has been sliced using all switches /ixy. All edges have been prepared for the overlap. Textures are 64x64. No stretching for this slice. |

This image has been sliced using no switches. While it looks the same as the starting image, the size has been adjusted to work in the game. Each square is 64x64 pixels. The total image is 192x192 pixels. |

A word more on streaking (stretching) vs wrapping (overlapping) the edges. Without the overlap, Slice60 just takes the outer 1-pixel row and copies it into two more rows. This makes the outer 3-pixels (rows) of the 64x64 image all identical. The corners are artificially filled with the single 1-pixel corner of the original image, so you end up with a 3x3 box of identical pixels in the corners. (Guess that's why the program calls it "streaked" hehe). Under some conditions this would often be unnoticeable for several reasons, but overall this would make visible the original tiling you might be hoping to preserve. There are probably too many variables to state a hard-and-fast rule about when or when not to leave a switch off. Let common sense be your guide. When you get undesired results, re-slice the texture with a different switch combination.

Please note that the switch options you use will depend on the graphic you design and what you plan to do with it.