declarer advantage
Declarer Advantage is the edge that declarer derives from an opening lead that is literally blind, hence imperfect, which lead often helps declarer more than it helps the defence. For example, a lead into a 1N/3N contract is essentially blind; the opening leader knows some general things about the hands but his lead can often be disastrous for his side.
When using Visual Deal's Double Dummy Solver, the lead by definition will be the perfect lead, and will erase the notion of Declarer Advantage. Any analysis you undertake will therefore understate the chances of making a contract by however much this advantage might be, because the double dummy leader will find any killing lead that might exist, no matter how bizarre.
Actually you can easily use Visual Deal to estimate this advantage. We have done this and it turns out that declarer advantage is a little more than 1/2 tricks on average.
We have included in Visual Deal the option of using a rule-based opening lead, with double dummy play thereafter. A rule-based lead makes a sensible lead based on the few things that might be known about the other hands based on the bidding, then leads maybe 4th-best, or top-of-a-sequence, or a singleton in a trump contract, or maybe top of a doubleton, the kinds of leads that you revert to in real life. This option is perhaps 2x as fast, and retains declarer advantage because it doesn't often result in that killing lead, so it is the option we recommend you use.