KJS for me.
Kjs offers a bit more variety of fishing i feel. Aston Park seems more directed/suited to the match angler and that approach to fishing. In my opinion, even the Lilly Pond has lost that secluded old estate lake feel it had for many years. Mind you Lake 2 at KJS, the big pond, has lost a lot of bankside trees etc. after recent landscaping.
My 14 year old son has fished KJS most days in the easter holidays and has had good fish every session, in some pretty poor weather conditions to.