For details see Intel Atom N270 vs VIA Nano vs Core 2 Duo vs Pentium M Benchmarks Performance
What c´t says (free translation, I'm not a professional translator...):
VIA Nano's new microarchitecture is a big improvement especially compared to VIA C7. This is confirmed by the CineBench R10: here the VIA Nano achieves double as much points as the C7.
... without HyperThreading the Intel Atom is much slower than the VIA Nano, even enabling HyperThreading the VIA Nano achieves better benchmarks results (Nano: 886, Atom: 843)
On the other hand, thanks to HyperThreading, the Intel Atom Windows system is more responsive than the VIA Nano Windows in case an application generates a high CPU load.
...With respect to CPU power both VIA Nano and Intel Atom can't compete with mature notebook processors.
...The Samsung NC20 doesn't have enough horse power to handle the user's manual: many seconds are required to leaf through it.
Bottom line: both Intel Atom and VIA Nano are low end processors, ok only if you want to use your netbook for email, casual Internet browsing and basic multimedia (MP3, video). If you want to do more buy a notebook with a decent CPU!!!!
Benchmark (CineBench R10) numbers
- VIA C7 at 1.6GHz: 406 points
- VIA Nano U2250 1.3-1.5GHz (in the Samsung NC20) : 886 points
- Intel Atom N270 (Hyper Threading not used): 545 points.
- Intel Atom N270 (Hyper Threading used): 843 points
- Intel Core 2 Duo T9400 (single core mode): more than 3000 points
- Intel Core 2 Duo T9400 (dual core mode): almost 6000 points
See also Intel Atom N270 vs VIA Nano vs Core 2 Duo vs Pentium M Benchmarks Performance