In terms of distance covered between January 1945 and VE Day, the numbers for the Eastern and Western Fronts are quite similar. This is an exceptionally wide question, and entire books can (and have) been devoted to in-depth discussion and comparison of the respective war efforts on the Eastern and Western Fronts. Perhaps unsurprisingly, a wide variety of strategic, logistical and, at times, political factors were critical in deciding who ultimately arrived at Berlin. Furthermore, while the Soviets certainly reached it first, the answer to your question will vary depending on the time period examined. Nonetheless, I'll give it a shot.

Numbers certainly played a part in the Soviet advance - and can simultaneously address your (correct) belief that a sizeable majority of the German Order of Battle was concentrated in the East at any given time. At the opening of 1945, while the Battle of the Bulge was beginning to wind down on the Western Front, Soviet front-line forces in the East numbered roughly 6,000,000 men to the Germans' 2,100,000.^1 In comparison, by February on the Western Front, allied forces numbered roughly 4,500,000 men to the Axis' 1,500,000 (this figured includes forces in Italy).^2 As these numbers show, the ratio of forces on each front is roughly equal - this, however, fails to reflect the military situation on either front. If anything, by February 1945, the Western Front was in an even more dire strategic position than the Eastern, and incapable of forming a cohesive defence.

Aggressive Soviet Strategy no-doubt played a major role, but the oft-repeated claim that the Soviets attacked using reckless human-wave tactics and showed no regard for the lives of their soldiers is, by and large, a myth. The rapid Soviet advance through 1945 stems from quite the opposite - mature and effective strategies utilising their massive numerical and logistical advantage to press, encircle and destroy German forces without the offensive losing steam.

A critical point that mustn't be ignored is the political aspect to the Battle of Berlin. Allied forces halted upon reaching the river Elbe around early April. The reasons for this remain a topic of debate, but it is widely accepted that the main reasons were thus: Neither the strain placed on Western-Soviet relations nor the projected casualties were worth the prize of Berlin.

As Beevor writes, " 'The lair of the fascist Beast' was the key symbol of victory after all the Soviet Union had suffered, and Stalin had no intention of allowing any other flag to fly over the city.".^3 Stalin's determination to be the first in Berlin, both for political and strategic reasons (Eg the extension of communist influence) meant that it would be an extremely dangerous political move for the allies to race Soviet forces there. In hindsight, this decision may have been politically naive, and certainly contributed to the state of Europe during the Cold War, but in the context of WW II, it was understandable.

Eisenhower was also prompted to call a halt to the advance and let the Soviets take Berlin due to the concerning casualty estimates he received. US General Bradley advised him on April 14 that taking the city would result in at least 100,000 allied casualties, though he later admitted that this estimate had been far too high.^4 He was, arguably, somewhat vindicated, since the Soviets suffered roughly 90,000 dead and 250,000 wounded in the combined battles of Seelow Heights and Berlin.^5

Hopefully this has done a little to shed light on the context of the two fronts and the reasons for the Soviets being the first to Berlin. Not exactly a world-class essay, but I'm procrastinating on an essay I really need to be writing about the Winter War.

1 -Tony Le Tissier, Zhukov at the Oder (Mechanicsburg: Stackpole Books, 2009), 13.

2 - David M Glantz, When Titans Clashed: How the Red Army Stopped Hitler (Lawrence: University Press of Kansas, 1995), 304.

3 - Antony Beevor, The Second World War (London: Orion Publishing House, 2012), 725.

4 - Ibid, 731.

5 - Michael Veranov, The Third Reich at War: The rise and fall of Hitler's military machine (London: Magpie Books, 2010), 583.