I've looked into this extensively.
Biden was operating under a larger national agreement between the US and Ukraine governments in which coordinated ambassadors and lawyers made agreements on what qualifies as corruption or not. The prosecutor being removed had recently undermined US policy in Ukraine. There was broad agreement that he was part of the old guard causing the problems in Ukraine. This was agreed by multiple EU partners and the US state department. Biden simply then pointed out that the guy undermining the US policy had to go.
This is what Trump is trying to claim he did. But he's doing so in retrospect and the timeline is problematic.
For one, no concerted Ukraine and American corruption investigation was ever launched via Trump. The State department officials who specialize in corruption in regards to US State department policy throughout the world stated during the recent testimony that no such arrangement had begun and that Trump's discussion or follow through did not in any way appear to be a corruption investigation as per the apparatus that is there for this.
Trump made his conversation and the freezing of funds independent of Congress who released the funds and independent of the State department who would be involved in the corruption investigations and then subsequent releasing of those funds if corruption was cleaned out. that is, again, nothing was set up to seek out corruption And with it release funds in response.
In fact, The funds were to be released upon only a public announcement of an investigation being started by the ukrainians.
Rudy Giuliani as a personal lawyer and not a part of government was used as a middleman to run messages. Again no congressional or state department involvement. Whether legal or illegal, there was clearly a shadow foreign policy being run here at that point. So at minimum, it's entirely different than Biden implementing a broad and cohesive effort on behalf of the United States foreign policy planning.
If the president holds up funds illegally (he did, That's why State department lawyers got them released not Trump), asks for a public statement of a corruption investigation in to the Bidens rather than simply start an investigation through the huge apparatus we have for this, and does so without notifying Congress or the state department, but rather via his non governmental lawyer...that cannot be reasonably conflated with a coordinated public facing international Western policy to fund Democracy (and aka anti-Russian) that has no end goal regarding political opponents.