Hi Hoblyman. Are you looking for a comparison for mounted or dismounted ? If you can a few days I should be able to help with a comparison of the mounted knights. I recently purchased a couple of sprues of the WGA and Victrix mounted knights to do this exact exercise. I need to finish gluing a couple of them up, but once I do I'll get a photograph posted.
First impressions are that the horses scale pretty well, although the Victrix are finer and more animated, similar to Perry WOTR horses, although the saddles are very wide and look oversized to me. The WGA horses are in more static poses and have chunkier legs. Conversely the WGA mounted knights are considerably smaller than the Victrix knights, which are on the large size of standard 28mm to my eyes.