Can't say that I'm a fan of deferring the pre-tax contributions. Among other reasons, our MAGI is right up against the threshold for the child tax credit phase out. Reducing our pre-tax savings would almost certainly bump us above this threshold.....which brings up another question of whether or not we should make my wife's IRA contributions to a deductible IRA instead. But that's another thread.
If you are in the phase-out range, you have a 30% marginal tax rate, not 25%, so the deductible IRA is better if you are eligible. For similar reasons, you should use the traditional TSP rather than the Roth. (You can always convert the deductible IRA to a Roth later if appropriate.)
This will also free up a bit more money for loan payments or 529 contributions, since you get a tax savings on the deductible IRA.
There seems to be a pretty clear consensus towards not foregoing the Roth space. What about the 529 contributions? We're currently putting $100 - $200 per month (on average) towards the 529 account. If I deferred that, we could probably eliminate the student loan in 42 months, if not sooner.
This makes sense unless you are losing a state tax benefit from the 529 contributions. Unlike the Roth IRA, you don't lose anything permanently; you can contribute later to catch up, and add the money which would have gone to the loan payments to your 529 contributions once the loan is gone.