I've put over 1000 miles across 3 different Power variants. The standard Power Expert hurt my sit bones even after a month, so I bought a used Power Pro Elaston and exchanged the Power for a Power Expert with Mimic. The latter is my favorite of the three.

Elaston makes the area supporting the sit bones a bit softer, which is noticeable on long rides. It doesn't alter the shape of the Power in any way AFAIK. It's still tricky to get the right saddle angle with both Power and Power Elaston. I find a more negative angle makes riding in the drops and my clip-on aero bars feel fantastic, but then I can't avoid slipping forward too much when riding on the hoods.

The Mimic tech was designed to support soft tissue without constricting blood flow, and also has tapered wings. Although it's marketed to women and I'm not one, I found it much more comfortable/forgiving to ride on the nose and at more saddle angles than the standard Power, which has to be dialed in precisely or else doesn't feel great.

When I had a bike fit I also tested the Power Arc, but felt that it didn't support me as well as the standard Power. I didn't have a lot of time on it or try many positions. Supposedly the Arc benefits those who want to move around on the saddle, so maybe it performs better in real riding conditions.