The best advice that I can give you is to buy what your friends and/or local club has and are presumably at least moderately happy with.
My local club has a Digitrax system, and while not everybody is happy with it, you can't make everybody happy anyway all of the time.
That being said, a fairly high number of club members have digitrax systems.
I went initially with a Zephyr system, primarily because it came with everything (including power supply), and has read back capability on the addressing.
You can add your analog throttle to it to control multiple trains, if you want. Then you can expand from there.
While I hear good things about NCE, but in my opinion, the accessories for it, like the auxiliary power booster, are TOTALLY overpriced.
If you outgrow the Zephyr, you can use it as an auxiliary booster, or a reversing booster. That's what I'm doing, after I upgraded to a Super Chief after having the Zephyr for 2 years. I'm expanding my layout with more locos and sounds.
You can also plug in throttles in the back of the Zephyr, if you want handhelds later, and the UT4 is only $65 bucks.