I have no experience with the SD light/hairball formula. When they very first came out with the hairball formula a few years back, they only had one formula. I tried it for T & P since Tubby was horrible with hairballs. It made him constipated, so I had to stop using it. Too much fiber for an older cat I guess. Now I believe they also have a senior hairball formula....but anyway....

What I ended up using for Tubby was the Petromalt you can buy at any pet store. It's a paste that comes in a tube. Tubby loved it and would eat it right out of the tube.

I think giving the new SD formula a try would be well worth it. Just buy one smaller bag, then if they don't like it or it doesn't work to your satisfaction, you can just switch back to what you're currently using for them.