Only you can figure that out. And, when you start to have kids, MFS will hurt you even more. There are a lot of credits and deductions that are reduced or disallowed to MFS. IRA contributions, dependent care credit, earned income credit, and many more.
Be aware of a few things.
IBR doesn't reduce your amount owed, it just lowers your payments and extends the length of the loan. Meanwhile, you are paying more income tax every year. Will the lower loan payments be worth the higher taxes, after 20 or 25 years?
If you think you might qualify for PSLF in 10 years, it might be a good investment to file MFS now and take the higher taxes and lower payments. But, any amount of loan that ends of getting forgiven will be taxable income to you in the year it is forgiven, and you will pay 22% or more of the forgiven amount as income tax in a lump sum due the year of forgiveness. Also, PSLF is practically impossible to qualify for, the paperwork is complicated and the qualifying rules unclear. As of September 2018, less than 1% of claims for loan forgiveness under PSLF were approved.
If you don't plan on applying for PSLF, then there is a provision (I think) that as long as you make all your minimum payments on time, your remaining loan will be forgiven after 20 or 25 years. That's a long time to pay higher taxes. Will the lower payments offset the higher taxes? And at the end, any forgiven amount is still going to be added to your taxable income.
That's assuming tax laws stay the for 25 years. The progressive arm of the D party wants more student loan forgiveness, maybe if you stall long enough you can dodge the loan. Assuming they win the presidency at some point and that their plans for free money for college kids persuade more voters than it angers. Or maybe there will be a R backlash against people who take loans, promise to repay, and then want an easy out.
My personal feeling is that if you promise to pay a loan you should keep the promise, and the faster you pay it the better. And I say that as a 53 year old with an outstanding student loan balance I am still paying on.
