If anyone with a similar concern was to ask my opinion (and I know you did not

), I would respond with a question: "Suppose you switch and a couple of months later the channels you crave are become available on Dish. Would you regret not waiting a couple of months?" Admittedly, no one knows when Dish will "catch up" to DirecTV, but they will before long if they wish to remain competitive. Surely each service will differ by a few channels, but the core ones will be the same. We have already been down this road in previous years with the addition of SD channels as both services grew.
Whether you are a Dish customer looking over the fence at DirecTV or a DirecTV customer looking over the fence at Dish, I believe the real issue is how patient a person is and how happy they are with their current equipment and provider.
In my case, I was with DirecTV before they bought USSB. I switched to Dish and have been with them ever since. It could have easily worked out the other way. Regardless, the viability of these two companies relies on them having very similar core offerings. The extra offerings (sports vs internationals, etc) are the differentiators. In the end, most people will be happy with either provider. Those that jump back and forth are usually the ones who cry the loudest and are the most unhappy.