Also, I think refering to Sp as a "cheap bow killer" undersells them. Against most opponents in the open, they're as good or better than Bd at a lower cost.
Against mounted, I would agree. Against Bw or light troops I agree. Against Bw(X/x) Bd are much better. Against Wb Bd are much better. Sp other then (S) don't have much chance against Pk (other than Pk(F)), but Bd can cope (or die!) Against Bd, Bd are certainly safer, but Sp might be able to get a result quicker - but it might or might not be the result the Sp want! Against other Sp, results will normally go with grade, but depth is important, particularly if you have to concede first impact.
So, whether Sp are better against "most opponents" in the open is certainly true in terms of the categories of troop-types, but whether they're better than "most" in practice depends upon what armies your opponents are using.
Let's not forget, too, that (a) Sp are almost always deployed at least 2 deep and lose a lot of their effectiveness if only 1 deep, so a strong formation of Reg Sp(O) costs at least 10 and probably 15AP per file. Bd on the other hand are normally deployed no more than 2 deep (because against foot they only need one rank to function properly), so a strong file of Reg Bd(O) is usually no more than 14AP, and
(b) we are only discussing effectiveness in the open. In rough, Bd rock.
Tim Child