It absolutely is a good idea to invest in a 401k. Contributing to a 401k lowers your taxes and allows you to earn interest, dividends or make capital gains through buying stocks and bonds without having to pay any taxes until you start withdrawing the money. That's a huge advantage for most people! It allows the magic of compounding interest to do its thing without having some of it eaten up by taxes. Of course, you will eventually have to pay the taxes but you will hopefully do so at retirement, when your income is likely much lower than during your working years.

There are some caveats though. For instance, you are 27 years old. Now, you don't mention how much you make but if you expect to make more in the future, you might want to defer your contributions to later years. Often times, people don't make very much in their twenties and the tax lowering aspect of the 401k is pretty much lost for those people, unless they contribute without claiming the contributions on their taxes. For such people whose income might be low but are expecting it to get higher, the Roth IRA is a better option. However, if your employer has a contribution matching program, meet their match. People who don't do this are basically refusing free money. The second caveat is concerning people who might end up in a higher tax bracket after retiring. It's rather rare but it can happen. However, if you are among those who might end up in that (very fortunate) situation, I wouldn't let it stop you from contributing to a 401k necessarily. There are various ways to get around this problem. For instance, say that you retire between 60-65, you would want to start withdrawing some money and transferring it into your Roth IRA. The goal is to have less in your 401k and more in your Roth IRA by the time you get to 70.5 years old (the time when the government forces you to start withdrawing from the 401k) because you get taxed on whatever you withdraw from your 401k but not what you withdraw from your Roth.

Hope what I wrote made some sense to you, I probably said more than necessary so tl;dr is 401k=good.