1) "Because most frozen fruits and veggies are frozen shortly after they're harvested, they're allowed to fully ripen, which means they're chock full of vitamins, minerals, and antioxidants, and freezing "locks in" many of their nutrients. On the flip side, much of the fresh produce in your supermarket was reaped over 1,500 miles away, and had to travel by truck to get there. As a result, it may have been harvested before it reached its nutritional peak, then artificially ripened during transport."
2) They're just as nutritious (or even more so) than fresh
"The differences above may be why frozen produce has been shown to be just as nutrient-rich, or even superior to fresh, a fact supported by two new independent studies. Scientists from Leatherhead Food Research and University of Chester, carried out 40 tests to measure nutrient levels in produce that had been sitting in a fridge for three days, compared to frozen equivalents. They found more beneficial nutrients overall in the frozen samples, in everything from broccoli to blueberries. In fact, in two out of three cases, frozen fruits and veggies packed higher levels of antioxidants, including polyphenols, anthocyanins, lutein, and beta-carotene. This conclusion supports previous research, which found that freezing produce does not destroy its nutrients. In one report, the vitamin C content in fresh broccoli plummet by more than 50% with a week, but dipped by just 10% over an entire year when frozen."
3) Frozen is additive-free
4) Frozen is already prepped for cooking