Okay so looks like we got same # for the weekly 30yr amm payment total (~$4050).
^ No. You are mixing up amortizations in your example.
Comparing weekly 30 year amortization to annual 25 year amortization: weekly is
less expensive on an annual basis simply because you are extending the amortization by 5 years. It has practically nothing to do with benefits of payment frequency.
A) Weekly 30 year amortization is $4,034 per annum, total repayment $121,025
B) Monthly 30 year amortization is $4,038 per annum, total repayment $121,132
C) Monthly 25 year amortization is $4,543 per annum, total repayment $113,580
D) Weekly 25 year amortization is $4,539 per annum, total repayment $113,477
You are comparing A) to C). You said "One seems to be paying less while still paying it off in ~25yrs due to interest savings."
This is wrong. You are paying it off
slower ie. repaying the loan in 30 years instead of 25 years
. The interest savings by having more frequent payments is pretty much zilch.
If you want a reliable comparison, look at C) vs. D). By increasing payment frequency from monthly to weekly you save $103 over the total 25 years of the loan. On an annual basis, you save $4. The big factor is the overall
amortization period, not payment frequency.
(slightly different than my answers above due to rounding)