I'll take the liberty of raising a question. I'm asking it from the standpoint of a ship modeler, but I think it's just as relevant in any other form of static scale modeling. Why balsa?
Balsa wood became the most common material stocked by hobby shops, probably as long ago as the 1920s or 1930s, largely because the most popular hobby in those days was flying aircraft models. Balsa has one great virtue for that particular form of modeling: it's extremely light in weight relative to its strength. (And the strength of balsa really is remarkable. Some years ago I helped my stepdaughter with a school science competition that involved building a foot-tall "tower" out of balsa strips no bigger than 3/32" square. The towers in the competition were weighed, and then subjected to heavy weights until they collapsed. The winner would be the one with the best ratio between its own weight and the amount of weight it withstood before getting crushed. The one my stepdaughter and I built weighed less than four ounces; the judges gave up trying to crush it when it withstood thirty pounds.) By the time I started getting interested in modeling, in the mid-1950s, balsa was the only wood routinely stocked in a variety of sizes and shapes by most hobby shops.
But the stuff has almost no other virtues. It's soft (to the point of crushing when attacked with any sort of cutting tool that's not really sharp and disintegrating under pressure of sandpaper), has a horribly coarse grain, and soaks up finishing materials like a sponge. And in a non-flying model the weight factor is irrelevant. I think it's safe to say that most serious, experienced scale ship modelers reject balsa completely. Model railroaders also rarely, if ever, use it any more.
I'm frequently impressed - even amazed - at the things flying model aircraft enthusiasts are able to do with balsa; they've demonstrated that, with techniques undoubtedly refined by years of experience, the stuff can be shaped and finished with remarkable precision. But I have to wonder: why use it in a static model?
Good hobby shops and mail order suppliers (especially those that cater to the model railroad trade) carry basswood in just as many sizes and shapes as balsa - and the price difference is minimal. (Some dealers in fact sell some basswood pieces for lower prices than balsa of the same size and shape. I don't know why.) Basswood is a good deal harder than balsa, has a fine, straight grain, and is much, much easier to finish. It seems to be the most common wood among railroad modelers these days, and is routinely supplied in the better American ship model kits. (Scratchbuilders in the ship modeling world tend toward genuine hardwoods, such as box, pear, holly, and cherry - largely because that kind of model frequently involves stained or clear-finished parts. The fine grain of those woods can actually be made to look like "miniaturized" oak or pine with minimal difficulty.) Beginners often get the notion that soft woods are easier to carve than hard ones. It takes just a little experience to find out that - at least when we're talking about balsa - the opposite is the case. Basswood is far more forgiving of mistakes and inexperience than balsa.
The foregoing, I should mention, is based on my almost-exclusive experience with American hobby shops. I have the impression that basswood is not as common in England. (American and British woodworkers sometimes use different words for the same wood. I think I recall reading that some British stockists refer to basswood as tulip.) I believe British hobby shops routinely stock limewood for about the same purposes as American ones stock bass. I've worked with a few pieces of lime; the stuff I had was quite nice, though a little "stringier" than the basswood I'm used to. (That sort of thing can vary a great deal from piece to piece. I have no idea how typical the lime I had was.) Limewood gets mentioned all the time in British articles and books on ship modeling; I don't know what British railroad modelers use.
I'm certainly not qualified to pass judgment on any modeler's choice of material; for most of us it's a hobby, and how we do it is nobody else's business. But I do suggest that anybody who hasn't tried working with a harder wood than balsa give bass or lime a try. I've never met anybody who, having switched from balsa to bass or lime, switched back again.