Increased latency w/ auto lip sync?

[Zapf]

I got a panasonic sound bar today that I can hook up with either optical, or with hdmi (via the hdmi port with ARC on it on my tv). I'm not sure which to choose though. When Panasonic advertises auto lip sync with their Viera Link (in this case between the panasonic lcd and sound bar), would it be safe to assume its only adding delay to the audio to match the video (presumably the same way the tv would do with its own speakers). I'm also worried since the input with ARC (hdmi 1) was a frame laggier than the other two hdmi inputs - I have no idea if that would affect output though.