The two biographies tell substantially the same life-story, which I shall not rehearse. The bookish, precocious child of thoroughly assimilated Hungarian Jews turned himself into a scholar of what was then called "the Orient," especially of ancient India and Iran, and the scholar turned himself into a remarkably driven and self-contained man of action. But Mirsky and Walker tell this story in rather different ways. To begin with, Mirsky takes 550 pages, Walker two hundred less. I have complained before about the length of contemporary biographies, so on that score alone I am inclined to be more sympathetic to Walker's book; which indeed I suspect is still too long for the story it has to tell. Mirsky tries to give us Stein's life as Stein saw it, to that end quoting extensively from his voluminous and unstoppable correspondence. (Evidently neither Stein nor his correspondents in England and Austria-Hungary saw anything incongruous in sending off a weekly missive from the middle of the Taklamakan desert, in winter weather so cold Stein's ink froze in its pot.) This also gives us a vivid sense of what the places Stein saw were like, something Walker's more concise narrative slights, though she has the advantage of having traveled to many of the same places Stein did. (It is only slightly unfair to say that, coming from her pen, the Taklamakan might as well be in Nevada.)
On the other hand, Walker brings out things which Mirsky, occupying Stein's perspective, misses: how Stein looked to other people, for starters. He was often a royal pain, always insisting on having things his way, not taking no for an answer --- and rarely getting it in the end. She is also better at fitting Stein's acts and discoveries into the larger pictures of which they are parts --- she tells us about the Great Game, about the early days of Silk Road archaeology, about why the RAF had those convenient air-fields in the Iraq for Stein's aerial surveys. And, conversely, she also says more about what we now know about the Silk Road and its cultures. (Mirsky, who wrote in the 1970s and died in 1987, is naturally at a disadvantage here.)
In the end, much the same figure of Stein emerges from beneath both pens. He was a man like a hammer --- or rather an excavating trowel. He had no interest at all, so far as anyone can tell, in sex, power, fame, luxury or excitement; money interested him only so far as the lack of it threatened his freedom of action. He formed some devoted friendships when young, but seems to have lost the power of attachment after reaching the age of thirty, even half-seriously regarding his successive dogs as avatars of the original Dash who accompanied him to Turkestan. (He would, however, make friendly acquaintances of men of all races and conditions, and would be strongly loyal to those who had served under or beside him, as he was to the empire whose bread he ate all his life.) Often loneliest when surrounded by people, he focused all his energies into his work --- and those energies were immense. He was dedicated (in several senses), methodical, meticulous, almost indefatiguable, unrelenting, a small, wiry man who made a career out of overcoming obstacles --- physical, bureaucratic, personal, even those of his own body and tastes --- by raw will intelligently applied. His desire really was for knowledge of the pasts of the great civilizations. Leonard Woolley said that he conducted "the most daring and adventuresome raid upon the ancient world that any archaeologist has attempted," and "raid" is just the right word, for he was totally unsuited to the prolonged sieges of exhaustive excavations of the sort Woolley favored, and not much more given to the garrison-duty of desk-bound scholarship, though he did that conscientiously enough, to ensure that what he brought to light on his raids (and brought back from them) became the common possession of the republic of learning.
I said before that Stein never took no for an answer, certainly not for a final answer. The extreme case was Stein's unending series of attempts, spread over forty-odd years of wanderings, to obtain permission to explore in Afghanistan, particularly at Balkh, the ancient Bactra, hoping to uncover the remains of the Greco-Buddhist civilization of Hellenistic Bactria. "My hope of reaching Bactria made me take to Oriental studies, brought me to England & India, gave me my dearest friends & chances of fruitful work, and for all this I must be deeply grateful to Fate" (letter of 1923, quoted by Walker, p. 248). I do not know what moral to draw from the fact that, in the last year of his life, he was finally invited by the government of Afghanistan, the "Promised Land" of his private letters, only to die a week after he arrived in Kabul, a month shy of his eighty-first birthday. "Hindsight permits the question: the promise given to Moses?" (Mirsky, p. 542).
On balance, Walker's book is better suited for general readers, Mirsky's for those already hooked on the Central Asian past. Either is eminently worth reading, but I cannot imagine why anyone except a fanatic, a scholar or a book reviewer would read them both.