Thinking about a new cup.

I've had my Diva cup small for about 4 years now, and its very discoloured and much softer than it used to be. So I'm thinking about getting a new cup of somesorts. I was wondering how all the design aspects of the cup effect its performance? So for those of you with multiple cups, how does each aspect effect its use such as insertion, suction, keeping in place, staining etc.

Length and Width are fairly obvious.
What does firmness effect?
What about size of the first and second lips?
How about positioning of the holes, number of holes, slantedness of the holes?
Texture?
Silicone vs Rubber?

I liked the length of the Diva Cup with the stem completely off,
I also was thinking that I could do with a wider cup.
I definitely wouldn't want any smaller, I like how much it holds.
But I found I didn't get very good suction with my Diva Cup and it discoloured really fast.

Thankyou :)