RBS reported revenues of £13.4 billion in 2018, with UK Retail Banking contributing roughly 47% of this figure.
Barclays' revenue in 2018 stood at £21.4 billion with Corporate & Investment Bank contributing approximately 46% to total revenues.
Barclays has a more diversified model as compared to RBS. However, RBS's focus on retail banking has helped the bank's revenues largely trend higher over recent years, while Barclays' revenue have stagnated
Despite RBS witnessing better revenue growth over the years, Barclays's revenues in 2018 were roughly 60% more than that for RBS.