Both plugins seem to be doing the same, allowing you to display different products as if they were variations of the same product. However the solution developped by iconic is less user friendly… one of the main problems being that on hover the main image does not change… that alone makes it not very usefull and does not offer the great user experience Linked Products swatches by Sweetplugins does.
And to kill it.. I will just add that with Sweetplugins you pay far less.. and get a lifetime license.