I am confident of my cost estimates because 1) I have taken the time to mathematically calculate expected cap ex 2) I have been doing this for quite a few years. 

As such, my belief is that the market price in any given local market within the US is probably the fair representation of its valuation, considering both future appreciation and current cash flow.A retrospective mathematical modeling of the past performance of various major US markets might be interesting.

It is simple math and growth rates (it is a mathematical fact).If you need the cash flow in the short term to supplement your income, etc., Coastal CA may not be the correct market. 

this simply is never talked about on BP.. its always what is mathematically best..

Of course it makes sense that a $300/month profit on a $20,000 investment is a higher rate, but you still owe $80,000 (assuming 20% down) so you're still not really making a profit at all mathematically. 

I want to know the answer mathematically and assumption based, before I make the decision. 

I seemed to have got the message very quickly that my math skills would never be appreciated in my family.My brother's BS degree is in, predictably Computer Science/Mathematics.

Mathematically with compound returns in time they will beat real estate even without leverage or cherry picking. 

If this method is able to save you tens of thousands of dollars as opposed to just keeping your mortgage and applying the over payments directly to the mortgage then your method should be incredibly easy to prove mathematically. 

The question you are asking isn't really a mathematical but from my point of view as a realtor most clients prefer Gas heat over oil or electric.