I would think at least some of the Nationals that went back to neon made bad choices in picking their led's, power supplies and manufacturers. The most expensive option isn't always the best option. LED's and / or neon need to be picked and spec'd for the job at hand, the proper amount installed, the right size power supplies/transformers as well as wired correctly with the right size wire. I've seen a lot of led letters wired incorrectly. They work but it's hard on life expectancy. Running power supplies to the maxx is another big issue.
I personally, have never had an issue or complaint with my led channel letters. I use 1 brand led's and 1 brand power supplies only and have for almost 5 years now. The main reason is we are wholesale and ship all over the US and I want to know what is in the sign and I want to know my customer won't be calling me for shipping damage or other lighting complaints.
If you do your own work and bend neon it's a great option. But, if you pay someone else to build the product and install the light source you should probably be using led's in most projects. We all know how employee's respect our product and tools. Once it leaves my sight I don't know how it's handled and every time you pay for a mistake you take money from your bottom line. With led's the installer can tie a rope to it and drag it to the job site and it will probably still light up.
On a side note, we converted our sign, a set of channel letters, to led's 5 years and 3 months ago. They run 24 hours a day by choice, to see how long they would last. They are all still burning and look pretty good. I'm sure the brightness has fallen off some but it's hard to tell when you look at them every day.