sorry for the late reply, I totally forgot about this website... oops. IMHO, I would use the 50mm very selectively. It is really no good for vlogging on the t3i. The t3i is a crop sensor camera which means the image will be zoomed in a bit. Given that 50mm is already a pretty zoomed in lens to begin with, the crop sensor definitely does not help. Also, since most vlogs are shot in tight, small bedrooms, it is very possible you will not have enough space to use it effectively.
As far as the "high quality out of focus look" (otherwise known as a shallow depth of field), It can get you that, but a crop sensor camera will also keep the background from being as shallow as the lens would normally allow.
To try and put it the easiest way possible, crop senor cameras come with a number that you have to multiply the focal length and aperture by in order to understand the full potential of the lens. I believe the number for the t3i is 1.6. This means that a 50mm lens is really an 80mm lens (1.6 x 50mm) and the aperture of 1.8 is really a 2.88 (1.6 x 1.8).
Sorry for the vomit of information. Basically, I would make sure your shot is well exposed and well framed before worrying about the quality of the background. If the 50mm won't work in the setting you film, I would skip it or invest in a full frame camera first.
