Padded saddle VS padded shorts Why do cyclists use padded shorts instead of padded saddle? It seems like putting padding on the saddle would be more optimal. Doubly so for triathlon.
Padded seats tend to have more padding than used at any given time. This pushes the other 'extra' padding into the soft tissues. This causes numbness and discomfort over time. 

So slim hard seats are actually more comfortable over time, if they are the right size. You need to make sure your sit bones (ischial tuberosity) are well situated. The sit bones of your hips are designed to support weight for long periods of time, where a plush seat disperses your weight to muscles and other areas.