Table of Contents

When assessing the usefulness of general purpose graphic software, pay attention on how lines are drawn. Lines drawn with pixels can not be adjusted.
Beziér and splines are constructed of 1 or 2 segments per curve. These segments are controlled by 2 to 4 logical points. It is OK for Torchon, but if you want to adjust a complex stitch or gimp for a more fluent result, you have to move many control points one by one. Most software especially developed for lacemakers, does not understand the behaviour of threads/pairs between pins.

Pixels

bitmap.gif
Bitmap or pixel oriented programs are good for processing photos. But not for scalable drawings. When enlarging pixels become visible, when shrinking dots may disappear. Drawn lines can only be corrected pixel by pixel.

Vectors

A more detailed explanation than below can be found at about.com.
bezier.gif
Beziér-line are defined by their end positions and two "magnets". They are scalable without problems and adjustable by moving the endpoints or magnets.

knipling.gif
Knipling somehow combines the "magnets". Therefore you sometimes need more parts to construct a desired line.

spline.gif
Splines are defined just by "magnets". They are less usual.