MCM requires subtraction, two directions, 1900 is additional, maybe multiplicative if you want to be strict, either way only one direction. I'm not sure what's "more direct", either is linear. I might even think of 15:45 as a quarter before 4 [1]), but I'd argue that subtraction is conceptually a level higher.
Nevertheless, high level representation might be an advantage. Maybe an interesting parallel viz. cognition is the 19.95 pricing scheme that's apparently proven to be confusing to the consumer. I'm just not sure which numeral system suffers more from that.
[1] which marks an isogloss between east and west germany, the latter saying "dreiviertel vier" - three quarters four; German also has a weird order for decimal place reading: 121=hundred-one-twenty
Well MCM is not how Romans would write this except in rare cases. That one did not become a standard form until Medieval Europe.
MDCCCC is absolutely a more direct representation of the counters on a counting board than 1900. Each letter precisely represents one counter and its position.
But if you want, you can make a counting board with a line down the middle and use one side for negative values, in which case MCM would be a pretty direct representation of that. (It is unclear whether this was the origin of such numerals; we don’t have a whole lot of evidence about how calculation on ancient counting boards was done, because it was largely part of oral culture.)
Nevertheless, high level representation might be an advantage. Maybe an interesting parallel viz. cognition is the 19.95 pricing scheme that's apparently proven to be confusing to the consumer. I'm just not sure which numeral system suffers more from that.
[1] which marks an isogloss between east and west germany, the latter saying "dreiviertel vier" - three quarters four; German also has a weird order for decimal place reading: 121=hundred-one-twenty