The 401 (k) is simply objectively better. Both 401 (k) plans and IRAs have valuable tax benefits, and you can contribute to both at the same time. The main difference between 401 (k) and IRAs is that employers offer 401 (k) plans, but people open them (using brokers or banks). IRAs tend to offer more investments; 401 (k) allow for higher annual contributions.
Your 401 (k) plan has limited investment options. In all likelihood, you can choose between mutual funds from a particular provider. However, with an IRA, you can invest almost anywhere. In addition, you probably have more types of investments to choose from, not just mutual funds, but also individual stocks, bonds, and exchange-traded funds (ETFs), to name a few.
A 401 (k) is a better option than an IRA if you want to invest more for retirement and aren't too picky about investment options. Most plans are limited to the securities (such as stocks and bonds) chosen by the employer.