Disclaimer: I have had only limited exposure to the new VEX IQ parts, and have been VERY involved with FLL, as a competitor for 6 years, mentor for 2, volunteer judge and referee for 3, and summer camp instructor for 3.
It is important to recognize that in cases like this, there is no right answer, as each team’s situation is different. You have some good examples of this in your last post, regarding local availability. However, you asked for my views on the two programs, so I’ll give them. Based on my experience with FLL, I still very strongly recommend FLL over VEX IQ for most people. Here are a few reasons:
-The VEX IQ platform is certainty well designed. However, it suffers from being the new kid on the block compared to LEGO much like Tetrix did when it took over from VEX in FTC: because it is new, there are relatively few mechanical components, even if some of the core hardware capabilities seem improved. This problem is compounded on itself by the veritable juggernaut that is the LEGO back catalog: more than half a century’s worth of plastic parts, in hundreds of thousands of variations.
-Besides the obvious improved selection, LEGO offers a more subtle related advantage, which in my opinion is decisive, when considering what we are trying to achieve: kids are familiar with it. Most kids who will come into your teams, no matter what platform you choose, will have played with LEGOs. Many times, they’ll bring in their own kits to contribute to the team, and use mechanisms inspired by their own LEGO kits in their robots. Not only will they be familiar with how they work, but it’s a GREAT way to pitch the program; I can’t tell you how many kids sign up for my LEGO robotics summer camp almost entirely on the basis of seeing the word “LEGO” in the catalog. To these kids, its a smooth transition from playtime to serious robotics competition, a transition that I could see being much more jarring if you present them with an unfamiliar platform.
-Mindstorms is doubtlessly a quality platform as well, and as mentioned, quite battle-tested. If you haven’t yet, take a look at the new EV3. Some impressive new capabilities.
-Even moreso than in VRC, in FLL/IQ there will be a WIDE range of skill sets, from teams that can hardly do anything, to teams that can do it all with ease. FLL has a proven track record of being FANTASTIC at dealing with this, with numerous missions with varied difficulty. The quality with which VEX IQ’s more VRC-like approach, with a few repeatable tasks, deals with this remains to be seen.
-As mentioned, FLL forces autonomy, which I think is valuable for students at that age. Students who have FLL experience are FAR more likely to seek out/use sensors when they graduate to VRC and FRC than those who did not. Relegating autonomous to a side-competition in VEX IQ hurts this.
I judge these presentations every year. This post…how should I put this…this is not a good post.
FLL’s target age is the same as VEX IQ. Namely, the target age is kids. The competition is designed around this fact. You may feel embarrassed to have dressed as alien elvis years ago, but trust me, there are literal tens of thousands of kids each year having a BLAST doing similar things at their competitions each year. The FLL research project is a FANTASTIC way for kids to have FUN doing this stuff, especially those who may not be immediately attracted to building and programming robots. FLL teams I’ve been involved with have brought in many kids who may not have done the program otherwise through these projects, and they are just as inspiring, if not moreso, than the robot game. And every year, I leave the judging room grinning from ear to ear, inspired by the students who were inspired to sing me Gangnam Style parodies about using robots to help seniors. 
Finally, I want to end with a word of warning to this community, about some of the verbiage I’ve heard about VEX IQ and FLL. It is great to be enthusiastic about a new program, that’s what will help it grow. It is great to think one program better than another, we should all objectively analyze these things when making choices, and strong competition will create better products from all parties in the future. However, I’ve been seeing a disturbing trend, of people not just hoping for the overall success of VEX IQ, but people hoping that it achieves this success by achieving “victory” over other programs in the process. This line of thinking, and targeting existing programs for conversion rather than starting new ones, is downright dangerous to the mission of both the RECF and FIRST: To make STEM education accessible and inspire students. Fewer than 10% of students currently have ANY access to ANY of these programs, and spending any energy on converting one program to another is energy that could have been spent tapping that 90+% untapped market. I’ve made clear that I am a strong FLL supporter, but I would NEVER walk up to a happily functioning VEX IQ team and try to get them to throw away their VEX IQ parts and buy brand new EV3s. Spreading VEX IQ is great, but always remember the bigger picture.
