A so called inland application has the criteria that the applicant is living in Canada and must continue to reside in Canada during the application process.
An outland application however does not require that the applicant stays outside of Canada for the duration.
For an outland, the application is processed in Mississauga + the applicants home country visa office. The applicant may be in Canada, their home country or a 3rd country or travelling between.
A couple of years ago, the processing time for inland was very long. Now it has gotten shorter. It can be a difficult decision knowing which type of application to go for. With inland, you can have first stage approval and an open work permit in 6 months. However, if it goes wrong and they want an interview, your partner is stuck in Canada waiting for a year or two or three and unless she finds a way to get a work permit or study permit, she'll be sitting around doing nothing. With outland, if it goes wrong, it will also add time to your processing time but your wife could then leave, go home, find a job etc. if money is tight. With outland, there is no open work permit available and although it is most common that visit visa are extended for outland applicants, it's not guaranteed.
If your wife may be travelling back and forth for the next year or two, I think I would recommend outland for you but if it is very important for you that you must stay together no matter what and you make enough money that she doesn't have to work, I think you should go for inland.