Upvote:3
Like most hotel chains, they have a number of different sub brands at different price points. Some will be "hipper" or noisier than others, some will be in different parts of town (near the business and financial district vs near the tourist attractions, for example.
It is a good idea to understand, say, the difference between a W and a Westin, and in the same way to understand the difference between a Radisson Blu and a Park Plaza. You are unlikely to learn that from their 1 paragraph blurbs, though keywords like "luxury" and "midscale" provide clues. Try some bookings so you can compare prices, locations, etc. Look at the pictures for the style and the vibe. Then you will know what each sub brand means.