Rancho 9000 on long arm, 5100 Bilsteins on short arm, comparable front and rear springs, same tires, Goodyear MTRs.
I'm currently changing the 08 to a RK 5.5 longarm with currie RJ 60s, and fox coil overs.
This isn't my first experience with the long vs short arms, I also own a Jeep shop.

 

It's all in the set up and what you want to do if you crawl and have plans later of coil overs you go long arm all the way. What your forgetting is down travel you can set cool overs with less lift and still have 12" of travel. You can set it with 4" of up travel and still have 8" of downward travel. Now as far as mid arms compared to a budget lift. With the same 4" lift my buddy with a BL got 620 on a articulation ramp and me with a MA I got 935. Now I love my super-flex mid arm but I will switch it out later when I put on coil-overs.

 

All I can say is this: try driving a long arm. It's a different and much better ride, and articulates better too, even at 4"

 

And now this thread has come full circle.

 

[QUOTE=GJeep;3379564]What is "lower suspension heights"?

A lower height might be 2.5" inches of lift as opposed to 6".

 

As you must know, shocks have crucial influence on the ride quality. It's enough to re-valve just the up OR down resistance to chance the ride feel.
It's impossible to assess the ride difference on two Jeeps with different shocks.

 

Remember that this started as a reply to the OP question:
In this context, I replied that there would be no advantage to long arms.

I was unhappy with stiffness on my previous JKU. I checked every possible option, including long arms.
Tweaking the shocks seemed the best way to start with.
First, I re-installed the stock shocks, checked how they felt compared to the new Fox shocks, and checked their valving data.
This gave a starting point for re-valving the Fox shocks, tweaking the up & down separately.

I finally got what I wanted -- a ride which was soft enough on road, but still good for offroad, including 50 mph sprints on trails (while rarely hitting the bump stops).
The end result was better, on both trails and roads, than a similar 4" lift JKU with long arms but different coils.

The OP asked about long arms for 2.5" lift (and probably no sway bar disconnect!).
To that, I said no. He would have gained nothing from long arms.
I think that the full potential of long arms is at more that 4" lift.

By the way -
My full set of 4" lift 'all-adjustables' Full Traction and Fox shock w/ reservoires is very good, but I consider the EVO bolt-on coilovers. What holds me up is that I didn't have a chance to actually test drive a JKU with those, so I can't know if or how much better would the coilovers be.

 

Coil overs are a world of difference, as is longarms.

 

Having switched from the lift your talking about to the bolt on coilovers on my rig. Its a big difference in ride quailty. On road and especially offroad in the desert washes you will notice a big improvement.

That being said, the Full traction kit is a nice riding kit. It just cant compare to the Coilovers

 

Are you staying with the current height or are you planning on lifting it up more? TeraFlex has a 2.5" long arm specific upgrade kit #1955020 $2123.99. Honestly it would be overkill for a lift this size.