I have a T2i and use only the center single focus point. I don't remember the path to set it but it was easy, figured it out in just a few minutes of pushing buttons. You may need to be in a different mode than "Auto" to get there., I believe "Auto" may use all the focus points. With your T2i you can set most the same settings as you can with the 70D.
The 70D does do more than the T2i, but if you are not into video save your money until you have learned the equipment you have. The T2i is still a very good camera; the sensor on the 70D is said to be a little better than the T2i but not much and definitely not worth the cost if you already own a T2i. Move up from the T2i when you have learned what your camera can do and find it cannot do something you want.
I did move up to a 7D, but only because I found I was losing shots of Birds in Flight like I really enjoy. The processor speed just wasn't enough to keep up with the continuous shots I needed for Birds in Flight. Now I keep both my T2i and my 7D with me as the 7D is set for wildlife with a telephoto lens and the T2i is set for walk around with the EF-S 15-85. The T2i takes just as good an image quality as the 7D, it just can't keep up with the Auto-focus and processing speed of the 7D.
If you do not have a specific reason to move up learn how to use the equipment you have first. My son is a professional photographer and that is the advice he gave me - I believe it is the best advice I have received.