I've used a B17 for years and was reluctant to try the Swallow because it would be to narrow. Boy, was I ever wrong! I liked it so much I have three of them. I do recommend that the Swallow be used with a handlebar at least one cementer below the saddle height.
This is my second Brooks. My other one is a B17 on a singlespeed road bike. I was concerned that this one would feel different. IT DOESNT! I knew the first 1 mile that it was the perfect choice. I have it on a singlespeed track bike and was told this was better then the B17 due to the more agressive riding position. The advice proved correct. If you are looking for a Brooks saddle for an agressive bike like a track or tt bike, this is the saddle for you! If you ride on a bike with a more upright riding position, then choose the B17 instead. Enjoy it! I will never ride a different saddle ever again. Oh and I have quit wearing bike shorts since changing to Brooks saddles. and I ride centuries and Metric centuries.