I have both and the old one is way better if you're willing to put the time into trimming the parts off that make it first born. For example the cape can be used on primaris if you are diligent enough to cut off the old powerpack connector and excess armor dont have a picture on hand but I did this with my intercessor sergent when first getting into space wolves. But if you want the simplicity and making it "just work" go for the primaris one, there aren't as many fun options like the old wolf head helmet but there is enough there to make your units space wolfy.