More axle movement, more shock movement, based on geometry, a little more shock movement for a given wheel movement, some ability to improve geometry. A smooth suspension requires a range of shock movement. Starting off with a greater range of shock movement makes a smoother suspension possible. Or at least that was my take away from several hours of reading. Another comment I think I recall is that given stock shock travel, it is hard to significantly improve on 5100x's (sure there are probably better shocks available, but they don't offer much more juice for a lot more squeeze) When you outboard, you have more opportunity to make something like a 12" tuned Fox 2.0 RR shine. When done right, a lot of posters will say stuff like - I never realized a TJ could ride so well.
Or from a more pessimistic viewpoint, while you have the opportunity to improve travel and ride - you also have the opportunity to mess things up worse.
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I already know I want to outboard, but also understand I have a lot of work to do first to make it a worthwhile long term investment. I need to deal with tires, gearing and lockers, bumpers, winch, and armor first. After looking under my jeep today, I am pretty sure I need to fix my existing lift first-probably fix my steering first. I will also be dealing with my hardtop first. Once I get all that done, then I can worry about attempting to outboard. Meanwhile, the couple hundred that 5000x that Rancho's cost will probably be an immaterial expense compared to EVERYTHING else that comes before outboarding.