Student loan interest is on top of standard. "The student loan interest deduction is claimed as an adjustment to income. This means you can claim this deduction even if you don't itemize deductions on Schedule A (Form 1040)."https://www.irs.gov/publications/p970/ch04.html
So 22k of income for 2015 really isn't worth getting the 5k deduction in my opinion because your tax rate is only 15% (so amounts to less than a $800 tax refund). It's almost a 100% certainty that you will be paying more than 15% in tax when you are withdrawing your retirement funds and paying tax (traditional IRAs are pre tax money and you pay tax at withdrawal; ROth IRAs are funded by post-tax dollars and you withdraw the proceeds tax free). This rules out a traditional ira at least in comparing roth ira vs traditional ira imo (let me know if you agree Tiago).
If you don't have any money in the market, I'd get a roth IRA because a) stock market is low right now; b) it's a solid tax investment vehicle to diversify with since you may never have this type of sweet offer again (essentially you are investing $6,325 (you paid $800 of tax on that $5,500 youll deposit) for what should amount to about $30k after 25 years based on the history of the stock market (SP500 index). Not having to pay tax on that 30k would be sweet as hell.
Just investing the money means you are gonna lose about 1/3 of that 30k to taxes so 20k after 25 years. I'd rule that option out completely too.
As a biglawyer or SA person, you can get a 25k credit card limit with ease, so 5k to your nest egg just sitting there is way too conservative imo given your education background and how young you are should anything happen. Also, with at least another year of school, way too early to be setting aside nest eggs and losing money just on time value of money. Also, if you are in a big city, the 5k isnt really going to do much towards a house or something that can provide a return (avoiding rent) because downpayments are a lot bigger and so that's just a drop in the bucket (5% or less of just the down payment).
THe last option then is using the money to pay down a student loan. YOur loans are so low that I think you are going to pay them regardless of your career path and especially if biglaw. You lost out on the student interest deduction for 2015 though because that had to paid in calendar year 2015 (IRAs have that extra incentive allowing one to contribute to a 2015 IRA until April 15 2016). I would actually probably take a dent out of your student loans at some point in the not too distant future given your soon to be income in 2016 (or not borrow loans is preferable but not sure if you already have something covering that tuition since your debt is so low).
I think this comes down to 2015 Roth IRA vs 2016 student loan money. I lean 2015 IRA because it's very low investment even factoring in pretax dollars and paying student loans now at this point gets you your student loan interest deduction in a year whereas paying your student loans later this year gets you closer in time to the deduction. It's a little more aggressive, hard to quantify how much more so because the return is up in the air whereas student loan is a set return. The safer bet is student loans and locks in a return of whatever your interest rate is plus some refund for student loan interest deduction. If your student loans are less than 5%, I'd def do the IRA. If over 7% its probably a lean to the student loans. 5-7% rate is a lot closer toss up.