Both or either! If you are asking this question, you are obviously someone who makes their health a priority. Both are great ways to get more nutrients in your daily diet.
Personally, I love blending. While juicing is great too, you lose a lot of the nutrients when juicing. Also, if you are juicing fruit, you are going to greatly increase the concentration of carbohydrates (sugar) to fiber ratio which isn't a good thing.
I have done both, and I've found that the taste is similar and if you like the thinner consistency, just add more water to your blender. I think it is easier to clean up after using the blender, than it is to clean the juicer.
Blending leaves all the pulp in which contains a ton of nutrients, enzymes and fiber. This helps balance out the fiber and carb ratio, making blending a better option in my opinion.
Most regular blenders are strong enough to mix lettuce, spinach and frozen berries. I have been using my Cuisinart Powerblend 500 every day for more than five years and it has worked great! I also use a Magic Bullet blender which is very easy to clean.
If you do use a juicer, I would recommend drinking smaller quanities than you would if it was blended because of the higher concentration of carbs and the lower amounts of fiber in it.