Having used both systems extensively, I decided some time back to stick with NCE. My first system was a Wangrow System-1 (built by NCE) 11 years ago. I bought a Digitrax to have radio when Wangrow/NCE didn't offer it. I used my own Digitrax system and have operated at a friend's house who has a large layout on Digitrax - up to 12 operators, multiple boosters, etc. I've also operated on one of the largest NCE installations, that being La Mesa Club in San Diego.
My Wangrow system was very old and only marginally supported by NCE, with Wangrow out of business. In 2006 I made the decision to buy an NCE radio system and subsequently sold my Digitrax stuff, all except for one DT400R to use as a guest operator. I have the 1.5 radio upgrade and I'm quite satisfied with the radio performance, but even before the upgrade I'd still have stuck with NCE. I also bought an NCE ProCab system to put on my workbench for setting up and programming locos.
I would recommend getting some experience with both systems before making a full scale commitment and see which suits you. Also, it depends on where you live... if you live in a "Digitrax Town", you'll find all the help you need available locally, but increasingly you can find a strong user base of both Digitrax and NCE in any major metro area. Cincinnati was about 95% Digitrax but that has changed dramatically in the last 3 years - especially since NCE brought out an entry level system.
Personally I find Digitrax geeky, fiddly, and the documentation is exasperating. The system and throttles (DT400) have improved, the docs has not. NCE's system is much cleaner, but IMO no less powerful. I've also sworn off Digitrax decoders. Those I have in place will stay there until they tee me off, or until the next routine maintenance for SuperFleet locos. All Superfleet, and all new locos will get NCE or TCS decoders.
Both systems work. If you take pride in learning complex button pushes and deciphering self-referencing, overlapping tables and user instructions, you might love Digitrax. If you just want to get up and running right away with a robust, reliable, comprehendable system... there's NCE.
Andy