The Rams should have an edge because the real reason they feel this confidence is because of the offense Waldron is installing. Yet this offensive scheme from all reports is a variation of what the Rams run under McVay. So in effect, the Ram D sees it every practice. Lots of movement (eye candy), tempo, not just quick snaps, but also no-huddle not allowing the D to substitute and multiple route options. Brian Shanahan ran a very simplistic, rhythm (i.e. slow) related offense. They have good WRs, a strong run attack and they have made efforts to shore up the OL. That said will it all be enough? Who knows.
Since the entire NFCW has seen this from the Rams for years it won't be anything new to their defenses. That said it's always about execution and with any new scheme there will bound to be mistakes. Can they survive those mistakes? Who knows. The Hawks will always be a dangerous team as long as they have Wilson, regardless of their scheme. He's the difference when compared to the Niners and Cards.
Both the Niners and Rams have the pass rush to dismantle any offense, but the Ram secondary is far better than the Niners.