I suggest you choose bifocals for they are easy to be get used to. You can make your bifocals glasses have two focal lengths. One focal length allows you to focus at distant objects, such as watching TV. The other focal length allows you to focus on closer objects, such as computer screen.
If you are only nearsighted, you don't have to wear bifocal or varifocal glasses. A pair of prescription glasses is enough for you. Just depend on the degree of your nearsightedness, you can wear them all the time. What's more, if you can see the TV or computer screen clearly without glasses, there is no need for you to wear glasses when you watch TV or use a computer.