The south has the pool, and a bar on the roof. I think only the north has a gym. Apart from that both buildings have slow lifts, but those of the south wing are overtaxed, dealing with 20+ floors: so long waits. Both have variations in room sizes and view, with twin-tower views at a premium. Avoid the single rooms, which come with queen beds, but are restricted in size. Breakfast won't win any prizes, but its OK, and is the same in both - but i have a definite preference for the ground-floor restaurant in the north wing.

Apart from that they are much of a muchness, run by the same teams. If you are staying more than a single night, you might split the stay between the two to take your own sample. When there are stay points' bonuses the hotels are used to guests shuttling between them .