Marcus I value and respect your advice and opinions and would not randomly offer a post just to be argumentative. I do question the OP if he is pricing a 2.5" lift if he is serious about a 4" down the road. I don't have a dog in this hunt and will not make one cent if he goes one kit or the other. I would however offer some fools advice that if you are serious about going bigger later, then just save and do it all at once. If that is not an option then I would offer up the Synergy 3" or the MetalCloak 3.5" Duroflex kit. I just can't see buying something that is not really what you want in the first place.
The reasoning behind going with a 2.5" now is because this a sport wrangler with the less than desirable Dana 30 in the front. Eventually, this axle will break, or bend, or something. That's when phase two of my build comes into play. I will be sourcing a junkyard set of 60s, or comparable one ton axles, while I wheel the current setup. I will build the axles as I go, and then, when the time comes, I will swap axles, and go to the full 4 inch height I want with 37 inch tires. So if I'm being honestly, I want a mild off road toy that I can daily drive without too much hassle. Since this jeep is brand new, I'm not exactly chomping at the bit to start gutting axles, and my bank account isn't exactly up to the task either. Hence, why I am going to slowly source the parts I need, and build the exact axle I want. The entire idea behind this jeep is budget friendly. I know Jeeps are expensive, but I know from prior experience I can do a lot of this myself, and I have the skill set and tools to do, or learn how to do most of the work.
As far as the type of wheeling, I have looked long and hard into the kits, and it seems 2.5 inches is where most people keep the daily driven jeeps that don't see too much off road. I live in Las Vegas, so it's mostly desert style wheeling on rocks and sand. This is no means a crawler, and wont be for some time. Mostly highway miles to work, and the occasional weekend warrior type trips. But I want to be able to enjoy the jeep at the time same time. I fully understand I am essentially wasting money right now, but I'm OK with that.
Also, I notice you mentioned the RK fan boys. I find each company has their set of fans, and to each their own. I'm ideally looking for people who have run multiple lifts, and have something to compare. I thoroughly read through KJeeper's thread on another site about his lift kit he suggested, and he makes very valid points to back his suggestions up. That's why his "lift kit package" is one of my choices.
My goals for this point in my jeep include at least, or better, road manners than stock, mild flex, and retain-ability (meaning I can keep most of the lift kit, and swap certain parts to go bigger). I hope I make my choices a little clearer and easier to understand. My goal right now is to run the 35s I currently have, have mild flex, and keep the jeep somewhat daily derivable.