Thanks for the reply. Actually, the integrated chat features of either program makes it equally useful for roleplaying or combat. Whether you're looking at a social or a tactical encounter, the purpose of these programs is to make encounters easier (both for the GM and the players). As with everyone here, my time is at a premium, so this is a good thing.
Anyway, I may have answered my own question, so I'll post the answer as well:
Both programs allow the players to connect to the GM's computer as the game server. Klooge Werks seems to offer more features to those wanting to customize the program to their specific campaigns/systems. OTOH, it also demands more in terms of licensing and system requirements (i.e., the players also run the program on their computers--GM + 4 players = $100). ScreenMonkey only requires the GM to purchase a license, and allows the players to connect through any web browser (I use Mozilla Firebird/Firefox, and it worked fine for me--GM + # players = $32). One of my players has a fairly old computer, so I'm going with ScreenMonkey.
At first glance, it looks good. It allows for the importing of custom map images and the GM can determine how much (or how little) the players see. Chat features can also be customized, and the program incorporates an integrated dice roller. Even if you view combat as a burden, I think anyone running an internet campaign would find a program like this useful. It would obviously allow you and your players to get through the tactical sequences more quickly, so you could get back to the stuff you really enjoy.