Help:Advantages of OmegaWiki over Wiktionary
The main advantage over Wiktionary is for translations, and concept related annotations.
Number of edits
For example, consider "car" (en), "voiture" (fr) and "Auto" (de), which are three translations of a single concept. To enter these words in Wiktionary, you would have to edit three pages "car", "voiture" and "Auto" in each Wiktionary, i.e. a total of nine pages to edit. In "en:car", you would also indicate that "voiture" is a French translation and in the German Wiktionary "de:Auto", you would also indicate that "voiture" is a French translation. The number of edits needed goes up exponentially with each additional language considered (NN for N languages). Correcting a mistake that has propagated to other Wiktionaries becomes a lot of work.
At OmegaWiki, the same can be done with only one edit. You edit the concept corresponding to "car", and give the three words as translations of that concept in the respective languages.
Indicating several synonyms for a single concept is also one edit in OmegaWiki, and several edits in Wiktionary (one for each synonym page). Indicating a hypernym is also only one edit in OmegaWiki and will affect all languages.
Quality of the definitions
Regarding definitions, it becomes easier - and more necessary - to avoid circular definition with OmegaWiki. For example, at Wiktionary, "cunning" could be defined as "sly", and "sly" could be defined as "cunning". At OmegaWiki, since they are synonyms, they share the same definition. Therefore, if you define "cunning" as "sly", when you consult the page "sly", you would see "sly" as a definition, and it becomes obvious that it is a circular definition that should be changed.