Re-FI or Ride out the the ARM?

[Brandon Pearsons]

Currently I live in My principal residence which I plan on turning into a rental within the next year. 

I had a 5/1 ARM that went adjustable 5 years ago. The interested rate has been great! ->Currently the ARM interest rate is 2.8% ( adjustable to up to 2 points every two years. It is based on the libor index) Im loving the principal payment amortization of almost 50%! since I have had the same loan for almost 10 years.

My question is should I refi?????????????????????????????????????????????????

My payment will drop from $875 ( p&I @ 2.8% interest ) per month to $815 ( p&i @ 4.6%)  but my principal payment will drop only 27% since it is a new loan.  

I plan to hold and rent it out for a while! 

What is the smartest move?

a) REFI 

b) Keep riding the ARM for a bit with the low but adjustable interest and paying down the principal pretty substantially