What are the key differences between TurboTax and SprintTax for international students (F1 Visa) in the US, and what potential long-term consequences should I be aware of if I choose to use TurboTax, considering that some of my peers have reported higher tax returns with it?

When you are in the US on a F-1 visa, you cannot be considered a US Resident for tax purposes unless you have been present in the US for five calendar years. You are exempt from the Substantial Presence Test, which is not the same as exempt from US taxation.

Exempt Individual - Who is a Student

When you are a Non-resident for tax purposes, you are supposed to file a 1040-NR tax return to report any US-connected income. US Residents (for tax purposes) file a 1040 tax return. There are quite a few differences; one is that you can claim Standard deduction if you are a US Resident, but your deduction as a Non-resident is determined by the tax treaty (if any) between your country and the US. Also Non-residents are not eligible for education credits on their tax return.

Sprintax is one of the few software options that supports the 1040-NR, and it seems helpful but I've never used it. I believe My Free Taxes has a completely free option to file a 1040-NR, but doesn't have as much guidance.

My FreeTaxes

My Free Taxes is a free version of TaxSlayer, so you need to create an account with TaxSlayer for the self-file option. One of the first questions after that asks for your filing status - you would select Nonresident Alien there to go to the 1040-NR.

TurboTax assumes that you have determined you are a US Resident for tax purposes, and it's a common mistake for international students who have SSNs to file a 1040 when they should be filing a 1040-NR.

You should figure out your status and file the tax return you are supposed to. I can't say whether or not your seniors were correct to use TurboTax, but it's definitely not a good idea to file the wrong type of return just to get a bigger refund.

Long-term consequences - I'm not sure if there are any. I don't know how much IRS enforces this, if at all. It's possible it could affect you if you apply for naturalization, but that's something to ask an immigration attorney.