Your student loan interest is fixed, and you're paying it regardless of what happens in markets. You have no idea what might happen with investments. Sure, there are "historical" returns, or averages, or your own short-term experience, but who knows?

I was 24 once. I bought a house in the mid-2000's because it was a "good investment". Housing prices and 401K's were rocking. And 2008 hit, everyone's 401K dropped by 1/3, housing prices dropped by 1/3 putting us all underwater on mortgages, and a lot of people lost their jobs and had a hard time recovering. But student loans still had to be paid.

I don't mean to be negative, I'm just sharing the alternative to "Overall, I'm sure my investments can beat 4.3% yearly", as you said.

If it were me, I'd probably pay off the loans and start with a clean slate. Times are weird in 2020! There are people much older than you that are deferring students loans because of layoffs or job losses right now, and they had a "plan" just like you do. Gotta balance that risk vs. conservative (financially).