I had been using the Sonnox Oxford Limiter for a long time. Swore by it. Couldn't find anything else I could say even came close to matching it.
When I made the jump to X3, it didn't want to work right, caused crashes, etc. Also, I decided no iLok ever again. so, I started searching and tried about everything I could find that did not use iLok. I had it built up in my mind that something that was more expensive HAD to be better that anything less expensive.
As it turned out, I found the Concrete Limiter filled all my needs. And with no iLok!
The Limiter no.6 by VladG (a freebie) was VERY good, also but, the Concrete Limiter is so handy right there in my Pro Channel so, that's what I ended up with and am quite happy with it.