There is probably something under the tools menu that says "Thesaurus," although this is just a guess since I haven't used Word Perfect since I graduated from Windows 98.
I don't know about which is better either, but I do know that the Microsoft Office file formats are much more popular, and if Word Perfect doesn't support them, then you very well might be doing yourself a disservice in incompatibility.
I personally would recommend
OpenOffice. It seems to have just about all of the best features from each word processor, and supports just about every text format on God's green earth. And its FREEEEEE!!!
Jam it back in, in the dark.