Except RAM and Sense UI; Galaxy Spica pwns Tattoo. Sensi UI is good but sluggish & then Tattoo has only 256MB for it.
IMO if you are buying an Android device go for Samsung Galaxy Spica. It has got a bigger AMOLED screen, faster processor, xViD/DivX support, Android market, a patented sound engine etc. Android Market has lots of apps. that can only be enjoyed on a capacitive screen.
If marketed properly (looks like Samsung is currently intrested in promoting only
aam janta phones

) this phone will be a rage!!!