I went through this same decision. I am not sure I made the right one, but here goes.
I was torn between a 2005 non-sport and a 2005 sport for ~$1500 more. I decided to get the non-sport for a few reasons.
1. I was buying this as a 3rd vehicle, and I just didn't want to spend a lot
2. Having never driven a sport, I don't know what I am missing by not getting one with KDSS
3. While the KDSS system seems to rarely have issues, I was shopping in the 165k mile range and if there is anything that needs to be repaired, it can't be done DIY and it's an expensive repair.
4. I actually prefer the non-sport interior. I love that it feels like mid-2000s old-man luxury. I have newer cars with more modern interiors, so I wanted something that felt like it's era.
5. The non-sport was a 2-owner car and I was buying it from the 2nd owner while the sport was a 6-owner car and I was buying from a dealer.
However, I do sometimes question my decision for the following reasons.
1. I bought the non-sport sight unseen and I've already spent another $2000 getting the non-sport up to a condition which I want, so it's reduced the price gap between the sport and the non-sport already.
2. From what I've read, you can lift a KDSS truck up to 3 inches. Anything more, or long travel, you would need to remove it. I don't think I will be doing anything more than a mild lift.
3. I've been driving the truck a lot more often that I expected, and
I wonder how much less the KDSS truck would lean in turns. KDSS also offers better articulation.
That said, maintenance and condition is probably the most important thing. My truck did have a recent timing belt, alternator, radiator, and airbag replacement. Unfortunately it also ended up having a bunch of little things I wasn't happy with that probably didn't bother the previous owner. But who knows what was hidden in the Sport model I didn't see or end up buying as it's still for sale, months later:
Used Lexus GX 470 For Sale - CarGurus