@Killian Ankers This is something that just came up yesterday with a place I'm purchasing as a primary residence. right now its a 3 bedroom but we wanted to remove a wall on one bedroom to make it an open space office. My financer and real estate agent told me I should rethink that option because of resale/rental value for the future. We don't plan on being there more than 3-4 years (our little one will be starting school and we'd move to the burbs).
But as others have mentioned, the answer to your question is largely market dependent. In my case, my financer is looking at things very black and white - and the prevailing school of thought from that perspective is that 3 is better than 2.
If you buy right you could make the differentiation a non-factor and charge 2 rb rents for a 3 br unit which would make you much more competitive for folks looking for either or. Of course, this only if you're having a struggle getting a tenant in there.