The Elan is more difficult to throw around than the Salomon, but i wouldnt go as far as to call it a tank. It is a heavy ski, but there is so much energy in it, that once you get it going from edge to edge it is relatively easy to toss back and forth. The energy that can be found in the SLX T is above and beyond any slalom ski that i have skied. To compare the two to the 9S (2003 9S - never skied the 2004)... the 9S is stiffer than both from what i coudl tell. It is quicker, but requires you to be in the perfect position on the ski. The Rossi also did not hold an edge like the SLX. They were the least forgiving and most difficult to control for me... a heavier skier may have found otherwise. The SLX prefers that you are aggressive on it, versus the Salomon letting you relax a little - it does more work for you than the ELan... in the course anyways.
Out of the course, i would argue that they will perform equally well, but i would not recommend the S-LAB slalom for free skiing. The night that i tried them out, there was a lot of fresh snow around and because they were so light they got kicked all over by the loose snow. The Elan is stiffer so it tracks through cut up snow much better, but it is still not a ski that i would recommend free skiing on. The Salomon really made everything fall right into place for me int he course. I do not know if it is truly a superior ski as far as performance, but i think it has a good mix of high end performance in terms of edgehold, rebound, and amount of use input required, which all put into one ski for me seemed to be a faster ski. For any good slalom skier, i dont think that the Salomon would hold them back in the course at all. The difference was simply that you didnt have to push on the ski as much to get it to turn. Once you had your edge set you could really hammer on the edges, and feel perfectly comfortable.