I have a set of Monroe Reflex on my 88 XJ which I installled a couple of months ago. I love them. I installed the blue monroe matics 3 years ago, and only put 30,000 on that set.
The XJ rides more solid, I don't mean harsh. The suspension sucks up the bumps in the road but the passenger cabin feels like you are very solid. It feels very similar to my 01 Buick Le Sabre with the Grand Touring suspesion yet goes off road like it always has.
I took my XJ on a 1200 mile trip a week or two after I installed them. It was 500 miles one way. I was not as "beat up" after the ride. I was checking out our farm 80 acres and I need the XJ to ford some creeks to get to the land.
You should see an improvement in your ride with any shock you install but for the extra $40 I'd go with the Reflex.
Put on your long term project list these things, after I did these the ride was better and the XJ drove like it was on rails:
* Front control arm Bushings
* Front and rear sway bar busings
* Rear leaf spring and shackle busings
If you do the front end work you will think you have a new XJ. I also recommend a steering box brace, it takes out any movement due to pot holes or RR crossings. If you want to know more, just ask.
I am glad I did all the things listed, it has renewed my 88 XJ for another 15 years of service.