Heloc v cash out refi

We're planning a couple of renovations in our house. Forever home, these would be last big planned updates. Love our neighborhood. Current loan is 434k rate over 6%. With these updates, value would likely be 750-800. Original purchase price was $560k.

We're thinking of using cash out refi for half the funds, if we can get a lower rate in the process in next few months, towards 5.5%. when I look at helocs, the rates are variable and start around 9%.

Obviously we'd have a larger loan, but plan to go from 30 to 20 year. Any thoughts we might be missing here in considering other options?