As far as dry foods go, I think RC is fairly good but I think there is probably better out there or at least the same quality for a lower price. I know a few peeps on here feed PAH own brand (in the silver bag) which has pretty much the same ingredients as many of the premium brands. I'm not all that familiar with dry foods as I feed mostly wet food (all wet for Jaffa except for a few kibbles in his treat ball and half and half for Mosi at the moment). I generally feed Encore dry from Sainsburys (the same as Applaws dry) or Orijen - both high meat content and cereal free.
As far as dry v wet goes, I favour mostly wet food/all wet food for cats as water is so important and cats aren't great drinkers. With dry food, they have to drink a lot of water. It seems daft to me to take the water out of food and then go to great lengths with with water fountains etc. to try and get it back into them when you can just feed it along with the food. Dry food is linked with obesity because it's so easy to over feed, especially with premium dry foods as they are very calorie dense. Many people claim that dry food is better for dental health but there is no evidence of this and many (most?) cats swallow dry kibble whole anyway. It's also much easier to add medication to wet food. Dry food is convenient to be left down for cats that can regulate their intake or for when you're out.
I would continue feeding the RC dry if they are happy with it (although might be worth looking into other dry foods as there are more cost effective options out there or you might like to try them on something like Applaws/Encore/Orijen) but I would personally try to add some wet to their diet if they will eat it.
I would never take a vet's advice on nutrition tbh (except for the management of medical conditions, and even then probably only temporarily whilst I researched the condition) as I don't think they get much training in nutrition and many just recommend Hills or RC as they get lots of reps selling those and even sponsoring their training.
