If your using ham radio it would work pretty good. However you cant use digital modulation on GMRS or FRS.
If you have the money for NXDN or TRBO stuff, why not get a ham radio 70cm portable ICOM IDAS digital repeater, and set that up with an portable base antenna at your car in the parking lot, giving you your own personal ham repeater to give outstanding results.
I have used MotoTRBO at WDW and it works slightly better than narrowband analog. It's say that all other factors being equal, I get a 10% improvement in range. What seems to make more of a difference than analog versus digital is VHF versus UHF. UHF seems to work better in the parks.
Thank you for your post on how well the MotoTrbo works at WDW. I was thinking of using it when I go there soon, but if you feel it only gives you maybe a 10 % increase in range, then maybe I will try NexEdge at 6.25 and see if I get any better results.
If you're a ham just use the onsite ham repeaters that WDW has on site last time I checked Disney had two, a 2 meter repeater and a 440 repeater, never tried out the 2 meter one but the 440 worked well in all 5 parks, In Magic Kingdom where they are doing construction for I think the little mermaid (was back in may) near the race way was a little spotty for the 440 machine.
Icon idas works well in the parks. I did notice greater reliability of the radios vs a cellphone. I have a sprint iPhone and the service at the parks was terrible. This is where the radios came in very handy. I do realize that Disney has sprint/ nextel towers there, but their phones get priority over everyone else. That may have contributed to my very poor service. Basically use radios vs cellphones. Also there are GMRS repeaters near by for those of you who are properly licensed to use them.
I used analog in the parks many times. I found the coverage to be terrible. The only have great coverage with digital. I have made this a personal project of mine to always have great radio coverage at WDW. I have sprint cell coverage and its horrible there. Text messages take 10 minutes to go through. I have iphones. Call the cell it goes straight to voicemail.
I needed reliable coverage so I take a few digital DMR radios with me. They work great as stated. I would like to know if anyone has used Nexedge or IDAS.
I find WDW as being the perfect testing ground for digital radios. There is so much RF interference. there from the rides, parades and other electronics that if your radios work there they will work well many places.