Melonite (Salt Bath Nitriding) will vastly increase the hardness of the barrel, without changing a single dimension. Chroming a barrel will increase the internal dimensions of the barrel, which is why a chrome-lined barrel will usually be less accurate (they have to actually over-bore the barrel to allow for the dimensions of the chrome lining). Salt Bath Nitrided barrels that I have shot have lasted over 6k rounds with match accuracy (across-the-course shooting out to 600 yards). Chrome lined barrels are normally reserved for less accurate applications that require extended durability (combat arms, etc). One major consideration is that a SBN barrel is supposed to be "shot in" before you have it done...after it's done, there is absolutely no opportunity to fix any mistakes (a rough bore, a short chamber, etc). You also can't set back a SBN barrel (i.e. cut it back and rechamber it when the throat erodes).
fa18hooker is right on the money with his advice.