As I already said, I personally would prefer mediawiki engine, also because I daily visit
wikipedia. Wikipedia comunity is huge and IMO mediawiki engine is more mature, with obviously better functions and support.
About switching, I do not know how many content do you have here on bot-united wiki, but sooner you switch, less data you would have to convert.
Wiki syntax is somewhat similar between different implementations, so porting data manually should not be very tough. (I do not have personal experience with this admining wiki though)
BTW If you don't know wikipedia, go
visit it. It has articles about everyting. From common stuff like
glass, actual informations like
recent tsunami to highly specific articles for bot coders, like
A*,
Hash tables ...