I've both an Elite-18 & an SLX-18 next to me right now.
I won't have chance to use the pole properly until friday, but my initial impressions are:
1. The SLX but cap is much better. Not that I have ever worn one out, but I do see comments on forums about them, and the one on the Elite pole isn't nearly as substantial as the SLX one. Its a very small point though.
2. The SLX is 180g lighter than the Elite, that's approx 10g per foot. Its not a huge figure, but it is noticeable. The Elite-18 is actually slightly (30g) heavier than the CLX-18, though it is much more rigid.
3. The SLX-18 has a shorter closed length than the Elite-18 by about 90mm, mostly due to the clamps on the SLX being more compact.
4. The SLX-18 is a little slimmer,.. still comfortable to grip, but this is probably the main reason its lighter.
5: The Elite-18 is approx 40mm longer when extended
6: Rigidity,.. its hard to tell categorically when dealing with only 18' poles, but both seem fairly equal as far as I can test them (Put the brush on & swung it round a bit). MUCH more rigid than comparable CLX or HXTEL poles. Couldn't really ask for better.
7: The Elite clamps are larger,.. but my Mrs reckons they "look" better & stronger. They don't have thumb adjuster bolts like the SLX, but all Elite poles will ship with a fancy keyfob with an alan key built into it, so you'll always have the adjuster tool handy.
8: The Elite comes with a screw thread top, and the SLX comes with an extra quick release clamp on top. Weight wise there probably isn't an advantage in either, but the quick release is nice.
9: The SLX has positive stops, & the Elite doesn't. Its only a bit of sticky tape, so you can add it to the Elite if it bothers you.
10. The carbon weave looks very similar on both poles,.. almost identical in fact.