The Unicomp is a much heavier keyboard, in terms of the keys. It also feels more "crisp" at each key press.
The Topre feels much smoother, but definitely lacks in the tactility department, as well as in the auditory feedback department.
I love them both, and I switch back and forth between them with no difficulty. There are times when the Topre is better, and times when the Unicomp is better. A lot of it is mood, but there are also external factors, such as noise. The Topre is basically silent, compared to the Unicomp.