Best map for Russia?

I already use iGO but someone tell me Sygic have better maps for Russia.
I never bean before in Russia and i need good maps for russia truck.

I read somewere Sygic use same maps (here) like iGO but size of maps is diferent.
Russia for Sygic is >1.1gb but for iGO is <800MB (latest maps).

Can someopne explain that and tell mi which maps is better for trucks and why?

Thanks