Using a Heloc for down: 10% down with PMI or 20% down?

[Karen Hu]

Newbie here under contract for my first vacation home to use at STR!

I can put 10% down-payment using my HELOC (interest payment $113) with a PMI ($142) or 20% down payment for $225 —Mortgage rate 30-year is fixed at 3.125% regardless of 10% or 20% downpayment. 

The 20% downpayment ($225) is be less out of pocket loan costs than 10% route (113+142=$255). 

Which would you do for your purchase? Is one more tax-advantageous than the other?

HELOC rate is variable so there is a risk this will go up
—I have a pretty large HELOC so the 20% option still leaves me a good chunk for more investments or rehab costs.