Netduino

I have been using Arduino only for three weeks and I found it incredibly simple to use (I finished my project using Ethernet shield, UDP protocol, two gas sensors and an IR sensor attached to it, in the spare time of less than two weeks).

Yesterday I noticed Netduino and I am very impressed!
The computational power of Netduino fairly outperforms Arduino. I am a C# developer, and so I really appreciate Netduino.
The thing that shocked me is that Netduino costs only 8? more than Arduino (30.96? from coolcomponents).

Now I am very undecided: shoud I leave Arduino alone, and dedicate myself only to development with Netduino?
I am wondering what are Arduino advantages over Netduino.

Maybe the cost, since an AtMega328 with Arduino bootloader costs as low as 4.80? (the lowest price I found at the moment), while I can't still find an AT91SAM7X512 with bootloader alone.

Another point is that the AT91SAM7X512 requires SMD soldering, while AtMegs328 not.

My question is : are there applications where Arduino is best suited?