As Red Ranger says, it's all about the weather. We've been up three times from Sidney, twice in a Ranger 27. The upside to the west coast of the mainland (albeit after Vancouver) is that there are more anchorages and marinas to duck into along the way and wind blowing up or down Georgia Strait (on either side) makes for an interesting (occasionally hair-raising) trip.
On the east coast of the island it looks faster as the crow flies from Sidney, and the trip through the Gulf Islands to Nanaimo via Dodd Narrows (need to time the passage for slack if you do) has lots of interesting stops and easily within a day from Anacortes, but there aren't a lot of marinas between Nanaimo and Comox and you still have to cross over.
Most people I think make Lund their last stop before Desolation but if you're in the vicinity or coming from Comox don't forget Refuge Cove in West Redonda - a quirky spot on the edge of Desolation, great for supplies and a coffee, and an pleasant contrast to the monster ships elsewhere in Desolation (Prideaux Haven).
In Canada the Dreamspeaker guides are quite useful for local knowledge and colour. Safe travels.