LX7 or GF3?
Not really true,a very modern sensor against an old sensor even's up the playing field a lot,the LX7 can shoot at 80 iso,the GF3's lowest setting is 160iso,that's one stop straight away,unless you put the Panasonic 20mm lens on the GF3 with it's f1.7 you prob will be losing almost 2-3 stops against the more common 14-42mm lens and the 14mm f2.5 lens with no IS,LX7 has a good 2 stops of IS to fall back on for non moving stuff .
I have had the GF1,GF2,GF3 and still have the GX1,the LX7 is a far nicer camera to use then the Gf3 and Gf2, in RAW files the difference is about 1.5 stops in noise control.
In jpegs the LX7 is far better then the Gf2 and GF3,the jpegs are poor,the LX7 has the best Pasnasonic jpegs i have ever seen.
Unless you want to put other lenses on the GF3 i would go the LX7 route, i personally find the LX7 to be a excellent allround camera,my GX1 is used with a 14mm and Olympus 45mm.