I've had the good fortune to see Samantha Womack (Janus) doing proper theatre ("South Pacific" at the Barbican) and the misfortune to see Amanda Holden gracing the stage a couple of times as well, sadly. Most recently in "Stepping Out", fortunately I hadn't paid anything for the ticket, and even so I left at the interval, it was that bad. Since you're comparing the two, Samantha was excellent, Amanda was an absolute talent vacuum. I've no idea how she manages to stay on Britain's Got Talent when she herself has none. Or why the Daily Mail keeps bringing us pictures of her latest desperate mutton/lamb style, I guess she pays them to.