I had a really hard time deciding between the Vararam Air Grabber and the MOPAR Ram Airflow. None of the others appealed to me because the stock box is so well made and the other ones just didn't seem to do much of anything at all; some of them not even offering any changes to sound (which is what most people say is the only benefit you get anyway). To address your question:
I decided on going with the MOPAR Ram Airflow. (but it was tough). Here were the pros and cons lists I had made. I am sure there are more of each, but these were the things that mattered to me, so YMMV.
Vararam pros:
* Significantly cheaper ($330-$370ish)
* Nice 'old school' look. I personally like the look of the exposed filter; Especially with the Hemi Orange cover.
* Well documented HP gains. And even if *I* don't get the full 30HP, getting half of the advertised amount is still more than the full advertised amount from many other options.
* Additional 'dam' in front of the radiator to help direct the air. Not 100% sure about the effectiveness with this vs without it though.
Vararam cons:
* Not MOPAR, so the POTENTIAL for warranty issues (I know, I know, "they gotta prove it caused issues", but I have already been through an issue where my local dealership wouldn't even run a diagnostic because of aftermarket exhaust).
* Sub-issue with the above, but due to my dealer experience, I would need to uninstall the Vararam and reinstall the stock intake for each service appointment and then reverse the process after the appointment. Even if it only takes 30 minutes, that is significantly more opportunities for stuff to get broken/lost.
* Need to remove or modify the shroud. I don't think the shroud *technically* does much of anything, but it looks cool. And lets be honest, if you are buying a CAI, you care how cool it looks (and sounds)
* Not MOPAR and I don't want my $50K truck with a 10yr bumper to bumper warranty being turned away because the service manager is a d*ck.
MOPAR pros:
* OEM product. No issues with dealer. I can't stress enough how important this was for *ME*
* It also looks really good. Different style than the Vararam, so its like comparing sweet apples vs tart apples, but I like them both for different reasons.
* Has similar (identical I think) performance gains to the Vararam. As far as I have been able to find, it is actually based on the Vararam anyway. The construction and design is extremely similar.
* Retains the shroud look (actually replaces the stock shroud, but the idea is the same)
* Plenty of space and opportunities for paint/decals for making the engine bay a bit cooler/different
MOPAR cons:
* Holy cow it is expensive. I paid $848 including shipping for mine. The day it shipped I did find a place that was within driving distance that I could have got it for $760 though....The cheapest I saw it was $730 but it had like $300 shipping so.....
So, honestly, if I wasn't so concerned with the potential warranty issues, I would have went with the Vararam. If you just have a standard warranty or have a good local dealer or for any other reason are not as concerned with potentially running into issues, then I would recommend the Vararam. But for me, paying $450-500ish more to be 100% sure that my extended warranty won't be denied in 7 years because I put on something that does not say MOPAR was worth it.
As for improvements noticed:
* Sound - Sound at idle is almost no different. Sound with low throttle, but still accelerating (like out of my driveway) has a nice sort of growl from the front end. Mid level throttle is overshadowed by my exhaust, so it is difficult to say if there is much of a change there. Heavy on the gas while on the highway/interstate produces a noticeable front end sound. I like it.
* HP/Torque - So...my truck has a full Kooks Headers and Exhaust system (headers, cats, mufflers, pipes) which dynos it at 450HP to the wheel already. While I have not had the truck dyno'ed since installing the Airflow, my seat of the pants dyno says: Not a ton of improvement until I accelerate over like 75-80 mph. and since I drive like 80% in the city, that is not often.
* MPGs - Here I can positively report that there has been a very noticeable increase. Prior to install, my average MPG was a steady 12.7 (remember, like 80%+ of my driving is stop and go in the city driving with plenty of idle time at lights). I have had the intake on for about a week and even with some.....spirited....driving to notice the sound differences, my average MPGs are up to 13.3. So not a HUGE change yet, but when the fuel economy is that low, an additional half mile per gallon average is decent. And I think it will increase even more if I can drive like a normal person....
In my opinion, I paid for peace of mind and to avoid hearing "I told you so" from my wife. I am not claiming the Ram Airflow is superior to the Vararam. Honestly I think they are probably VERY similar...except in cost.
Hope this helps.