The OP is "poll-worthy"
My personal take is that Hitler is going to do it under nearly all circumstances if he's conquered Western Europe. He'd probably dismiss reports or declarations of vaster Soviet armament.
The question becomes, what military misfortunes, stresses or circumstances could cause him to put off the invasion:
A) Failing to win against France? - that's probably fairly non-controversial
B) Japan and America enter the war pre-Barbarossa, especially if its a year or more early?
C) Britain and France go to war against the USSR over the Finnish War?
D) USSR joins the Axis after Fall of France and invades the Middle East?(Not bloody likely from the Soviet point of view), but theoretically Hitler may delay for a limited period to allow more damage to Britain and to see if Britain will come to terms based on combined German-Italian-Soviet pressures.
E) France fights on from the Med?
F) WWII begins over Czechoslovakia, 1938, not Poland, 1939. --Most likely leads to A), but say it does not and there's a miracle and Germany wins in Czechoslovakia in '38 and France in '39, but the war becomes a new "peninsular war" as it merges with an unfinished Spanish Civil War. The widened scope of the German commitment to southwest Europe, plus the probability that Poland is a neutral, really cuts off plausible pathways for a German invasion of the USSR.