if your intention is to use it «as it cames» then go for the NXT, it's a good way to start and somewhat less expensive.
But EV3 is much more than just a revised NXT. For me there are 3 novelties in EV3 that make all the difference:
- SD card
- USB port
- full Linux support
This summer I discovered ev3dev (Debian for EV3) and have been trying EV3 with almost every USB gadget I have with great sucess: Wi-Fi, wireless gamepad, 8-relay card, audio card, webcam, LEGOcam, Bluetooth 4.0, Wiimote, 1-wire master... It's like having a Raspberry Pi with a shield for sensors and motors, you can do in EV3 almost everything you can in a Linux laptop or a Raspberry (albit slower).
So for power users, EV3 is the horse to bet.