Informative topic breakdown of Cock rings:

Which pump is better?
I've been looking into penis pumps that use an air pump system, like the ones here on EF, but I've heard that water penis pumps are better for your...

What is the ring tone on your mobile phone?
Do you want a cool ringtone or is generic just fine?

Wedding Ring
Have you ever thought of your wedding ring as a symbol.. like a collar? I got my girlfriend a promise ring for Christmas and we're kind of treating it

Reccomend a pump that can be shared by a male and female?
I'm FtM (Female to Male) pre-op, and I've browsed for a clitoral pump for a few weeks now with not many promising products turning up. They all seem..

Binding during sex
Do you wear a binder during sex?

I have the Big O ring. It's not the best cock ring ever, but it is a good place to start. I love that it's cordless-that's very important for me.
In case of Diving Dolphin you have to deal with cords that, I can personally attest, are easily ripped out.

You'll get more intense stimulation and better settings with the Diving dolphin and multiple settings is a big selling point for me! And keep in mind that The Big O ring uses watch batteries which will be more of a pain in the neck to replace. So, I'd go with the Diving dolphin.

I have both kind of cock ring and I really enjoy both of them!

Everyone I know who has the diving dolphin LOVES it (including my best friend; I gave it to her for Christmas last year). I've heard some "meh" things about the big-O, but nothing bad. However, I've only heard good news from the Dolphin. Although Stojic is right; if it is important to be cordless, you probably want to go with the Big O.

The diving dolphin looks amazing!