用HELOC還房貸? - 美國

現在的房貸是 fixed rate 5.125%，
想用 Home Equity Line of Credit 還房貸。
做了一點功課，現在在考慮的兩個方案：

Background:
Prime = FED Rate + 3% = 3.25% today
Margin = up to the bank
APR = Prime + Margin

1. Harvard University Employee Credit Union
a. 4% today. Margin = -1.0% for the life of the loan if I maintain
a checking account with $1,500 balance, 0% otherwise.
b. Floor = 4%. Ceiling = 18%
c. $550 origination fee waived if initial withdraw > 10k
and keep the account for 2 years. No annual fee.
2. St. Mary Credit Union
a. 3.75% today. Margin = 0.50%. Margin may change any time.
b. No Floor. Ceiling = 12%
c. No origination fee or annual fee.

預計要借7萬到10萬。請問 1 還是 2？
有人有經驗或有聽過家人朋友用HELOC還房貸的嗎？
在美國找得到更好的deal嗎？

先感謝 m(_ _)m

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