At first, I thought this would be an easy, slam dunk question to answer at least from my perspective; however, when you peel this onion's skin, you definitely find several more layers of ideas to consider.
On the base level, my attraction to RW vs providers is virtually the same. I have to be visually and sexually attracted to the lady from a physical perspective. Yeah, I'm a male pig who is superficially drawn to physically attractive ladies, but that is at the base level. There is more going on than just the base level though.
Putting physical attractiveness aside, when it comes to RW gals, we have to mesh on so many different levels that I wouldn't even consider thinking about in terms of providers. For me, a RW lady personality, intelligence, values, interests, etc are all very important concepts that attract me to a lady. For example, I love sports. In the RW, I couldn't be attracted to a gal who hates sports or showed no interest in sports. For me, sports is a common ground issue. If we don't at least have this interest in common, then the attractiveness will wear off very quickly.
In terms of attractiveness (besides the physical) when it comes to providers, age plays a big role to me. I am attracted to the younger providers. Sure, there is something to be said for the experience of a mature provider. However, the mature providers are the ones in my age range. These are the types of gals I could easily pick up at a bar someplace. Sure it is nice sometimes to be with a provider of my same age range, but I find the younger ones bring something different to the game. Being in my 40s, I like interacting with providers in their 20s. I suppose if I can keep up with them, then I know I still have it
Also, I'd like to think that I can learn from a younger provider while also being able to pass along several lessons of my own.