caotropheus
ArboristSite Operative
Unless you're in a tree, you don't have a need for a top handled saw. They're not going to be any easier on your wrists, and are considerably more dangerous to operate.
Space, I do not agree with you in any point of the use of the saw. Top handle chainsaws are also known as pruning saws. They are very easy to handle with a single hand and are used for example for pruning orchards. With practice many operators use a pruning saw single handed and use the other hand to hold branches and remove them. The handle is build in such a way that the center of gravity of the saw is located some millimeters in front of the throttle. The only point I cannot comment is the potential danger of top handle saws in relation to other saws because I do not know the statistics.