MUD Error-- it also does PPC --- and registration is now free for those that don't have OS access to the App Store.
Weatherman displays a small tabbed window for each site you want to see. I have this and Seasonality.
Seasonality tries to show all sites in one window. Seasonality keeps an archive of the places monitored, visible by graph up to a year (scrollable further back, if you've had it longer. Weatherman can display about a day's worth of "trend".
Weatherman gives you chill factors --- Seasonality doesn't.
Weatherman gives you alert messages --- Seasonality doesn't.
Weatherman has a list of cities to pick from to monitor. It makes set up easy, if you know the geography/ city names of the area you want to monitor (you'll need to go "out there" to get the info you'll need to enter for obscure places. Seasonality also offers "quick-pick" locations -- with the addition of being able see and select monitoring stations on the map.
Weatherman has the option to show a variety of animated maps, were the info is available. Seasonality has a satellite based stationary zoomable map.