I recently installed the Art Vista piano. First time I've dealt with a Kontakt stand-alone app. Noticed something strange - the latency seemed a hair less in stand-alone than when I used it as VST (Forte as host) and also less than GS2.5.
Should I be taking drugs to justify my hallucinations or is this actually possible?
Latency depends from the buffer size used by the audio application. If the standalone app uses smaller buffers than your VST host then it's obvious that the latency is lower.
Since on commercial audio applications you don't exactly know how they handle buffering internally (eg if they use 2 or 3 buffers, if the buffer size settings do mean total latency or only one bufffer etc) it's not always straightforward to calculate exact latency.
You could experiment a bit by increasing buffers to a very big size and measure (for example with an audio/midi sequencer on a second machine) what the midi to audio latency figures look like.