respectfully sarah, kale can be tough and flavorless. it depends on the variety and growing conditions. otherwise, i'd agree that they are 2 good choices for greens. taste them first before buying.
i've seen the color in swiss chard runs out when cooked thru. it might retain some color if quickly blanched and shocked, tho. i dunno; never tried that.
i highly recommend that anyone with the availability of a garden try growing various greens in spring, as soon as the nightime temps are above 40F.
start with spinach, swiss chard, and individual or mixed leaf lettuces. graduate to head lettuce, escarole, arrugula, endive, and cabbages. if you have good soil and sun and few other gardens around (bugs), try broccoli and broccoli rabe, cauliflower, and brussel sprouts.
you'll learn about greens if you try to grow them, whether you like it or not. they're easy to grow, and are a good starter for a learning gardener. since they grow in short seasons comparitively, problems are evident and repaired quickly, in most cases.