Tourist or Visitors Visa?

[lovetolaf]

I have a male friend from Nigeria who wishes to visit me here in Canada.  Could someone advise as to whether he should apply as a tourist or a visitor to visit me.  With the tourist visa I would not be involved in the application but as a  visitor I will be issuing a letter of invitaiton.  I am a single female. Will they deny the visa if he comes to Canada as my visitor if they think we are in a romantic relationship?  Which visa would be his best chance to be granted a visa to Canada?