Pay down which mortgage account?

alex_163163

I bought a new house earlier this year, and sold my previous flat.
Due to the Erc on the mortgage on the flat, I ported that mortgage (£47k) and took out a second product (no fix or erc) for the remainder needed (£137k).
Now my fixed period on the £47k mortgage has come to an end, we have switched BOTH mortgage products to 1.99% fixed for 3 years.
I want to overpay on the mortgage (at the moment can only afford an extra £90 per month but I figure it will all add to the capital repayment), and trying to figure out which account it will be most benifical to overpay on? Or does it not really matter as the interest is the same on both accounts?
Option 1: over pay £90 per month on the £47k at 1.99%
Option 2: over pay £90 / month on the £137k at 1.99%
Option 3: overpay £45 / month on both

Any advice?

[Deleted User]

There's no difference.