You may have a point, but I still find easier to do
111
948 948
289 => 289
--- ---
1237
thanCMXLVIII plus CCLXXXIX => CMCCXLLXXXIXVIII => MCLLXXIXVIII => MCCXXXVII
but it may be that it's because what I'm used to.
Otoh, arabic numerals are a lot easier to multiply/divide. Before the wide adoption of arabic numerals all but the most educated couldn't perform simple multiplication/division.