The other thing is that Kenneth Branagh is an international star, thus his Wallander is more distinguishing and less team player: his colleagues have less importance and less time on screen than in the Swedish version. Branagh's Wallander is also more unsociable and seems more depressed, underlined by long scenes focusing on his face expression under driving or walking. The big plus is that the Brits have tried to create the Swedish atmosphere as much as possible, signs are in Swedish etc. Well, the UK and Sweden have same latitudes, so the filming of Swedish nature was also possible in England.
Nevertheless, if you like Scandinavian crime thrillers (with slower pace, minimum explosions/chases, long nature frames), then the Wallander series is definitely for you. However, the "trinity" series is better to watch in a temporal sequence, they have some references to earlier events.