That's not even a question.... if I can afford them, coilovers without a doubt. There's a bit more to their design than what meets the eye, even in my posts thus far... and it has more to do with than just the resi. Having delved into some suspension design in my day, I'd put the comparison between OME and Coilovers along the lines of the 3.7L QTI vs the 5.7L QDII in XKs. If given the choice, and money wasn't the main problem, the decision is easy.
Affordablity here is the key. Are they worth almost $1000 more than the OME setup? That's very dependent on what YOU want. Like doc said, a lot of us wont use these shocks to their potential. Want adustability? Throw a 1/4" spacer above the OME...done. Is the ride of the OME HD too stiff for you? Get over it... or spend the extra grand. Etc.
Ironically. ... Docs point works with his stuff too. I'm going to send probably 2 or 3 times the cost that I would for a Rola Rack to have him build me one.... and the overall difference in performance for how ill use it probably wont be much. So should I just get the rola? Not much different of a scenario here.. it depends on what type of build you're looking for. When we go offroading you're not going to say "damn I would have been able to do that if I had those coilovers". Its really the other features that you have to determine if they're worth it for you.
Adjustability, ride quality and bling are my 3 main reasons. I can wheel with my RC spacers and still do just fine on the trails. But building off-road rigs is one of my hobbies and also love going to truck shows. I'd love to build this XK to a point that's very functional and will also catch some attention at the shows I attend. We already know it'll catch looks offroading regardless of what suspension I put in it lol. And I do want to be able to tweak my ride height. We'll have to see what happens next year. I still have to save up for the SL first!
OK lunch is over.... back on the road. 2.5 hrs left to Norfolk.
Edit: got checked into hotel and put some extra thoughts in above.