No, it is not an improvement. The S6 is being updated more rapidly than the S7. In fact, as of now, the S7 is still running Android 6.0.1 Marshmallow, and the S6 is running 7.0.1 Nougat. Samsung has not been forthcoming with updates (quarterly security updates for the S7, no OS updates at all) or schedules (all they have said for over 4 months is "soon").
Bottom line, I would rather have stuck with my GS5 than move to the S7. It would probably have more recent security updates.