Mortgage on primary residence or investment property?

[Peter Rigakos]

Hello Everyone and happy new years.

Currently, I am looking for another rental.  I believe I found one that I would like to put an offer.  I know that it is much easier to get a primary mortgage as opposed to an investors mortgage as the rates, appraisals, fees...etc are cheaper in general.  My question is, if one was to pay cash for the rental, but keep a mortgage on their primary residence, what advantages are there when it comes to tax write offs.  I know that I can write off my mortgage interest in my primary residence, however, does it make more sense to write it off the income a landlord would make on investment properties?  Basically I am looking at the long run instead of the short term pain of getting an investors mortgage.  

Your help is great appreciated in advanced.