Ok, I finished testing with R700, 4870 CF, 3870 X2 and GeForce 9800 GX2 (Single and SLI mode) and recorded frametimes in Crysis and Unreal Tournament 3 demo:
The worst case scenario happened with 3870 X2 in Crysis when every other frame was rendered after ~21,5 ms and every other after ~49,5 ms. However in UT3 demo 3870 X2 provided stable ~11,5 - 12,6 ms rendering times between the frames.
R700 seems to be very strong and it rendered every frame after ~21,6 - 22,1 ms in Crysis and ~11,5 - 11,9 ms in UT3.
Also 4870 CF provided equally good results compared to R700 and rendered every frame after ~21,3 - 21,7 ms in Crysis and ~11,2 - 12,1 ms in UT3.
GeForce 9800 GX2 showed alot more variation in rendering times and frames were rendered after ~21,9 - 25,1 ms in Crysis and ~7,4 - 11,5 ms in UT3.
PLEASE NOTE!
These results are measured and analyzed with simple tools including Fraps and Excel. In my own conclusion, it seems that microstuttering depends on game engine and if we leave 3870 X2 in Crysis out from the results it looks like NVIDIA's SLI (9800 GX2) is suffering more from microstuttering than AMD's CrossFire.