You get much (much) better terms on a home loan if it is your primary residence. On your primary residence it is possible to refinance up to 100% of the value of the property and the rate is usually a good 1% lower than you'll get on an investment property. Typically, on a home that is not your primary residence you can only finance up to about 80% of the value of the home and the rate is typically higher.
For example:
If you live in a home that appraises for $500,000 and you only have a current mortgage of $350,000 then right now you could probably refinance that home at the full $500,000 value, get $150,000 cash out of the home and (if you have good credit) you can probably still get a 30 year fixed at under 4% a year.
Conversely, If you have a home that you rent out to a tenant that is worth $500,000 and has the same $350,000 mortgage then if you want to refinance that you can only take out up to 80% of the value. In this case that would be $400,000... you'd only be able to get $50,000 cash out in this scenario. Your rate would also likely be closer to 5%.
I'm not a mortgage guy so don't quote me on the rates. That's just an example.