I'm incredibly sceptical about Lampard.
He did fine with a Derby team that was expected to challenge for promotion (albeit the previous manager actually got more points than him).
He then got parachuted into the Chelsea job for a period where there was a transfer ban and fan expectation, plus the fact he's a club legend was going to get him some leeway. He did ok, they scraped 4th I think? Just about the minimum acceptable performance for them.
He then bombed the following season and a proper manager comes in, immediately turns it around and wins the Champions League, which gives you an indication of the strength of squad Lampard actually had.
The Rooney situation is the opposite. He's got a dreadful Derby team and his win % is awful, but that's to be expected. He's only managed 60 odd games so far and this season against the odds he is doing something special with them (they're outperforming their xG by a lot).
You're talking about one manager with 2 and a half years experience who, at best, has just about met expectation levels and another manager with just over one season under his belt who in terms of pure results hasn't done a great deal (but context needed).
Both are massive, massive punts. I don't want Duncan as manager, but he really doesn't seem like much more of a gamble than those two.
I'm genuinely surprised this is the route we are going down, because if we get this appointment wrong, we really might end up looking at relegation