I've never heard that some Hoyas need a different soil type than others; most potted plants I think (except maybe bog type or aquatic plants) need a soil that drains well and doesn't retain a lot of water.
I think I remember someone (maybe mj) telling me that Ruthie is a fast grower and prefers a larger pot so maybe that's why I put mine in a bigger pot fairly soon after I got it last year. I love the shallow bulb type pots for small plants and years ago I used them for Hoya cuttings and for growing African Violets.
My Ruthie is in a fairly large pot, in the mix I use for all plants, which is regular potting soil with lots of orchid bark mixed in; light, airy and well draining. I might un-pot her in the next week or so to see what the roots look like and if necessary move her over to a new container. I've never gone by the idea that plants "prefer" to be root bound but there may be many types of plants that indeed do prefer tight roots to perform at their optimum.
Hopefully, if you are able to get into contact with mjsponies she will be able to advise you on a correct pot size for both of your Hoyas. With a much larger pot I'd be watchful with watering; if the container is too large, the ratio of plant roots to the amount of soil could be too great for the roots to absorb all of the moisture, leading to water sitting at the bottom of the pot causing the roots to rot.
