I like Trotsky and all, and the simplistic analysis of his complex and often contradictory positions on most matters of import to the Union do him a disservice, but of all the available leaders of the 20s, Bukharin is by far my first choice. Trotsky was despised too much by the Politburo and had become too used to the use of terror and execution to re-order and discipline an organisation - though it was successful, and far less bloody than later purges, it speaks to a mindset that very well might deal with the eternal problem of the peasants by making war on them as Stalin did.
Bukharin was well-liked by... Everyone, championed a freer, more open style of Communism, could open relations to Europe, and was above all a smart, flexible, charismatic Old Bolshevik who could do great things. By the 20s Russia's cultural and scientific revolution was in swing and experiencing an incredibly boon even in the face of the post-war devastation and restrictions of the Leninist years, and a more balanced Soviet economy, almost guaranteed by Bukharin's policies, would not only improve its health, wealth and power in the shot term but likely guarantee the permanent survival of the Soviet Union and the Second World in perpetuity.