RStudio is an absolute killer solution from the get go. Package management in R is simple and robust. Shiny is the new Excel pivot table on performance enhancing code.
Python has more contributors, more users. It also creates a lot more noise. Business people may feel like it is a a programmer tool. R feel more approachable.
In the end, both are great solutions but we decided on R because we believe in the people contributing to the ecosystem, mostly RStudio. Somewhere down the line, there might be a transition to julia.
I believe both fread and readr::read_csv do the right thing here, but the base-R perspective on data manipulation before read.csv is to use Perl (the R-core team are pretty old-school, to be fair).
For a couple of years I have tried to excel macro myself a balance sheet template which does most of the copy pasting from precious years, does bank interest calculations and all.
It would be interesting to know how does a us CPA work because its all accounting package>excel>efile.