Malcolm, it depends on what you want to investigate, and where you live. It looks like you're Australian? I'm not the best person to advise on that. Different testing companies have different mixes of customer nationalities.
In general, if you want to verify all your ancestral lines, an autosomal test is best. Ancestry is the largest test provider, so they might be your best bet, although as I've said, it depends on where you live.
If you are specifically interested in investigating your paternal line (presumably McGrice, unless you know of an adoption or something similar in your line), then a Y-DNA test is best.
If you have a lot of money, I'd say take both tests, and then test some of your relatives, particularly the oldest.