I'm in my early 20s and want to retire around age 40

Hi,

I'm 24 years old and my wife is 23. We're both working full time and our combined salary is about $75k. My salary will most likely go up in the next few years and she's just now entering the professional job market. I have no doubts in three years we will be earning close to $150k-$190k a year.
We want to retire in our early 40s. I've maxed out our Roth IRAs and I'm about to max out a 401k.

Do you think we should go with a traditional 401k or a Roth?

I think your best bet is the Roth. You are in the 15% bracket right now. You save more money in the Roth, because it is after tax. Once you tax bracket is higher, you can switch to a traditional one.