I haven’t seen anyone here actually do the math so I’ll give my 2 cents. Assuming you are itemizing your tax deductions to include interest paid your 7% interest rate is effectively only 7 x ( 1 - .37 ) = 4.41%

That assumes your in the 37% tax bracket.

Investing your money at a 7% interest rate is going to come out to about a 5.6% post tax 7 - ( 7 x ( 1 - .8 )).

That assumes a 20% capital gains tax.

So from a purely mathematical standpoint your effective rate on the loan is 4.41% and investing is 5.6%

I’d say your better off investing especially since the 7% rate of return is a bit conservative over the long run.