From what I have seen and read, Giffords is in much worse shape than Johnson. Her appearances have been very carefully scripted and orchestrated. I think she has serious difficulties intellectually and physically. The Dems kept up this charade for a long time even suggesting that she might run for senator to fill Kyl's seat when he retires this year.
IMO Johnson should retire but the Dems don't want to lose the seat.
I saw Giffords on tv today, climbing up on stage for a campaign appearance. It looked like she was very dazed and confused and her husband was physically directing her where to walk by guiding her arm.