Sunglasses are quite essential to cut off the extra light because the pupil in your eye like the camera is used to maintaining only a certain amount of light which is reaching the retina. During daytime, it constricts and allows less light to get into the eye and at night it dilates and allows more light to get into the eye.
So if you find that you are in bright sunlight and you cannot tolerate it and you have to blink your eyes constantly plus, you notice your forehead wrinkles come up, do wear sunglasses because they definitely reduce the amount of light getting into the eyes.
Depending on the colour green, brown, black whichever you like and whichever suits you, use a suitable pair of glasses to try it out for yourself. The amount of darkening that should be used in the type of sunglasses is a personal choice. Some like it darker and some prefer it to be on the light shade.
Having said that, what is more important about sunglasses is UV protection. Polarized glasses or one with UV protection is a great idea. Polarized glasses help you to see very clearly especially while driving on a highway in the daytime or in the direction where the sunlight hits the eye the most.
So, even if cheap sunglasses can provide this UV protection then, using cheap glasses is not an issue because there is nothing about it that can spoil the eyes. Regular sunglasses of any make or any brand can serve the purpose considering everything else is a part of showbiz.
For example, say a pen or a watch is no longer meant to solve only the original purpose it was created for, the marketing world has made it to mean so much more to people. Basic items are no less than a fashion statement similar to the wearing of sunglasses.
In conclusion, none of these brands of sunglasses really matter. But, the usual concern that cheap glasses may not provide UV protection can be dealt with. So, go for a pair of glasses that has a Polaroid mark or protects from UV rays rather than looking for the mark of the brand.