Also the seeedunio doesn't have a standard barrel jack if you want to power it by anything other than from the USB port.
That said the seeeduino is very nice, the 3.3V mode + standard 0.1" headers are great features.
For my first arduino I'd buy the "official" board with DIP '328. This way you get the "standard" which everyone knows and understands, you can easily replace the chip, and importantly you support the original arduino creators.