Both of my charters off of the west coast/ukee area in the last 2 seasons we have anchored. And it produced great Hali numbers and quickly, sure we could have tried to troll or drift jig, but anchoring is the most productive way by far to catch them, if you can do it. Halibut work a lot on scent, and by anchoring and keeping the scent or whatever you are jigging in one spot it allows the Halibut to find your gear. BUt alot of the times due to current, tides, wind etc, anchoring isn't an option.
After reading these boards for the last 5 years, i would say the volume of Halibut in Victoria/Sooke area is less than what you may see on the west coast or up North, but the size of the Hali on average in the south may be larger. Most times whenever we have been trolling you catch smaller halibut 10-30lbs. The odds of landing the larger ones seem to increase greatly when you are anchoring. Of course there are exceptions to every rule, but this is what I have noticed.
Also areas like Nanaimo and southern gulf area, the Halibut population just isn't here, so anchoring can be fairly useless option and you are better off covering ground and hoping you get lucky on the troll and run into one.
Frankly anchoring is an intimidating option for most anglers and a pain in the butt. Guides that I know do it for a reason because it catches fish. But I would rather drift jig, and if it does work is by far the easier option, and that is why you may see people doing it up in the Nootka, North island area, where there is a plentiful halibut population with not the nearly the fishing pressure on it as the southern Vancouver Island area.