I guess we’ll just have to disagree. Go to a Greenland event pretty much anywhere in the country and you’ll find that WRC is used by the overwhelming majority of paddlers and paddle makers over any other wood (probably by at least 20-to-1). It’s only real deficiency is that it dents easily, but that can be mitigated by using epoxy-coated or hardwood tips, and perhaps edge reinforcements if you’re really hard on your paddles. I doubt that spruce is significantly better in that regard. WRC’s flex characteristics are ideal for a GP and can easily be tailored to paddler size and strength by varying the design. Stiffer woods are not necessarily better, as the can force you to make a paddle thinner than is ideal in order to maintain some flex and “snap” in the paddle. Personal preferences vary, but I don’t like a rigid paddle, which is one reason I’m not fond of carbon fiber GPs.
A great WRC paddle starts with a blank that’s quarter-sawn (“vertical grain”), that’s clear (no knots or pitch pockets), with the grain running as straight as possible from end-to-end. Like Greg, I’ve found that 4x4s give you double the chance of finding perfect grain compared to 2x4s. If you have really large hands or like a beefy paddle, a resawn 4x4 provides two blanks that are thicker than a 2x4. Another option is 2x6 lumber, which provides one paddle blank and enough extra material for the loom of a laminated paddle.
Whatever you choose, the key is to be extremely picky and not to settle for second-rate lumber. It’s worth investing the time to find good stock. Every broken GP I’ve seen has been made with an inferior piece of wood, sometimes also coupled with poor design. OTOH, a well-designed GP made from a good blank will last almost indefinitely.