I understand that at the beginning of the war the Soviets had superior armor but inferior aircraft and infantry. How did Soviet artillery and their use of it compare with that of Germany at that time? What about by the end of the war?
This source gives you an answer to your first question at least. It falls short of the second part of your question about the Battle of Berlin since it doesn't have case studies after 1944, but it might give you and indication.
Long story short the German author seems to have been fairly impressed by the Red Army's artillery employment. He does point out in the second case study for 1941 that it wasn't as flexible as German artillery usage. Though he also notes a number of instances where Russian infantry and artillery supported each other effectively so it wasn't totally rubbish.
In terms of technical qualities, I know off the top of my head the 'main' Soviet artillery piece, the ZIS-3, had a longer maximum range than its German counterpart (the 10.5 cm leFH 18). The source above seems to hint at this in one of the case studies where it seems German counter-battery fire was impeded by the distance of the Russian guns from the front line. Though of course the ZIS-3 was a 76mm gun and hence a bit lighter than its German counterpart so its not a simple question of one being outright better.