What are your thoughts on alder vs. the western soft maple?
I assume you meant to say
eastern 
.
I can't really say as this is the first Kubicki I've touched in over 15 years that one wasn't mine. I only just received mine on Tuesday so I haven't had a lot of playing time on it yet. I was able to find some descriptions and comparisons of both eastern soft maple and alder though...
Alder: Grows Principally the Pacific Northwest, where it is the most abundant commercial hardwood. Average height is 90 feet and the tree matures in 25 to 40 years, but will begin to deteriorate by 60 to 80 years of age. Alder grows well on burned over lands and thrives in areas that have been ravaged by fire, earthquakes or logging. Main Uses are for Furniture, kitchen cabinets, doors, shutters, moldings’, panel stock, turnings, carvings and kitchen utensils. Alder is used in the smoking of meats and fish. Red alder, a relative of birch, is almost white when freshly cut but quickly changes on exposure to air, becoming light brown with a yellow or reddish tinge. Heartwood is formed only in trees of advanced age and there is no visible boundary between sap and heartwood. The wood is fairly straight-grained with a uniform texture. Red alder machines well and is excellent for turning. It nails, screws and glues well, and can be sanded, painted, or stained to a good finish. When stained, it blends with walnut, mahogany or cherry. It dries easily with little degrade and has good dimensional stability after drying. Red alder is a relatively soft hardwood of medium density that has low bending strength, shock resistance and stiffness.
Soft Maple: It Grows Throughout Eastern USA, and to a lesser extent on the West Coast (big leaf maple). Average tree height is 60 to 80 feet. Its Main Uses are for Furniture, paneling and millwork, kitchen cabinets, moldings, doors, musical instruments, and turnings. Soft maple is often used as a substitute for hard maple or stained to resemble other species such as cherry. Its physical and working properties also make it a possible substitute for beech. Charcoal is often made from soft maple. Soft maple machines well and can be stained to an excellent finish. It glues, screws, and nails satisfactorily. Polishes well and are suitable for enamel finishes and brown tones. It dries slowly with minimal degrade and there is little movement in performance. Soft maple is about 25 percent less hard than hard maple, has medium bending and crushing strength, and is low in stiffness and shock resistance. It has good steam-bending properties
