Which one is the best Netgear Modem product----The one that is compatible with your isp. That's key. You can buy netgears best modem but have it not be compatible. Did you check with your isp on compatible modems.
and how long it will work efficinetly?---Until it goes bad. Sadly we can't predict that. You can do things to make it last longer like ensuring it has proper cooling/well ventilated (heat is death of electronics)
