a question: can you please define what do you meant by "didn't last very long" and also "cloud was not adequate". I think it might help troubleshoot the issue. posting a couple pics of the build would also be extremely helpful.
I find silica easier to use, but I prefer the performance/flavor with cotton. It's possible to use either of them successfully on the T3S, but getting great results with cotton might take a few extra attempts.
My suggestion is to try to be as aware as possible of changes made from one wick/build to the next. Try to be as consistent as you can, then do small adjustments, add or remove small amounts of cotton, always paying close attention to how much you used, so that you can keep track of how the last tweak affected your results. Notice how much resistance you get when you try to move it thru the coil, the length of the wick, if flavor wicks were used, etc etc.. With a few attempts you should be able to find your sweet spot and you'll probably get awesome results.
Another alternative, is to use cotton yarn, which makes things a lot more consistent. Personally I'm using organic cotton balls. If you decide to use cotton yarn, make sure to boil it first. (Boil it twice for about 20 minutes with some distilled water, and let it dry overnight)
hope this helps some, good luck!