I think that Jonze's movie operates more in the realm of surprise rather than suspense. The ending would be one location where suspense is evident. When Charlie and Donald are hiding out in swamp, there is suspense as to whether or not they will be killed or will emerge alive. There is further suspense as to which one will be more fortunate than the other.
I think that this element of suspense is reflective of the overall feeling of surprise in the film. The self- conscious way in which the issues of art, artistic responsibility, and personal identity are all woven together with the backdrop of Orlean's work and Kaufman's own is where the notion of surprise envelops the film. It is difficult to advance in its very nature. "Surprise" is something instantaneous, a momentary exploration of the unexpected. To sustain this throughout the film and continually build upon it is far more difficult than a particular moment of suspense.
In suspense, there is conflict building to one specific instant. Yet, in a work like Jonze's film where surprise is continually advanced throughout, maintaining something for an instant throughout the film is far more challenging and more innovative. It is here where I sense that surprise is more evident in the film and representative of the fundamental difference between it and suspense.