First of all...I have NOT ridden any Slash yet but just received my 2018 Slash 6 and 8. I have only ridden Pivot 11 2016 from Naish.
My impression by reading both user reviews and tests it definitely felt like the 2018 was worth the extra money. Being an engineer I feel that it's usually better getting a more refined kite that has been out on the market and where they have made improvements based on the customer feedback.
For 2018 that included reducing the diameter of the LE and changing the design of the wing tips. This was to make the kite faster in the turns and also fly a bit more forward in the window. I did read some negatives about the 2017 that it was a bit harder going upwind.
The tests I read on the 2018 was definitely better than for the 2017. Of course if you get a reply from someone who tried both 2017 and 2018 that is way better but it's usually quite difficult getting those reviews.
Here's what Real Watersports says between 2017 and 2018.
Insider Info Slash 2017
We thought that this felt like the best version of the Park that Naish ever made, so we tested it out with wake boots and some freestyle tricks. We were right, and it works killer for freestyle. There is very little power surge when you unhook, it boosts well, and it is just as much fun to ride on a twin tip as a surfboard.
The Slash is best suited for someone that likes a kite that pulls hard on the waves. It is not the best for the set it and forget it rider. When you pull really hard on the bar to send the kite through the wind window, you better be ready cause the Slash is going to turn and pull hard. Bigger kiters or people riding full power with straps will love the feel. If you are timid and just getting into wave kiting, you will probably want something less aggressive.
We were able to stall the Slash in the middle of a turn in a few instances. Most of the times this occurred when we were quite depowered, carving on the wave face and taking tension off the lines. The kite would change direction but then stall. This is pretty typical of most kites when the line tension comes off of them. There was still a little pull, so you felt connected and most importantly the kite did not back stall. The kite drifted really well and as soon as you got more tension on the line, you reconnected to the power without a massive surge of power.
We found that the Slash flies best with an inch to two inches of depower pulled on the 2017 Naish Torque Bar. We also moved the turning speed setting to max speed on the wing tip bridle attachment.
Insider info Slash 2018
The Slash is designed as a wave kite but it is an amazing all around kite for someone that wants a more aggressive version of the Pivot. We found that unhooked tricks and general free ride boosting with the Slash was a blast.
Compared to the Pivot, the Slash is a more aggressive kite. It has more direct feel to the bar, it is more power and is faster to initiate the turn.
The Slash has a fast to initiate pivotal turn. It does provide nice power through the turns that bigger riders and kitesurfers that ride with more power enjoy. If you loop the kite in the wind window you want to make sure you have plenty of line tension to get the kite to finish the turn. We found that if your lines slack out on a turn you might need to pull the bar float or edge to retention your lines to get the kite to rapidly complete the turn.
On one of the test days the wind had gusts up to 30mph and the lulls would go down to 10mph. The Slash handled the heavy gusts with out any issue. The QuadTex material allows the kite to keep the shape under the excessive load of these big gusts. During the really low lulls we found that the kite stopped moving forward. It didn’t fall out of the sky, but you needed to pay more attention to the kite in extreme gusts.