Some differences that stand out in my mind based on things I've witnessed:
- Dice mechanics. On a MUCK, you have a lot of leeway if you can get someone to code the system in. At that point, you can enter a command, possibly with some variables, and get an answer. For a tabletop game, you have to realize every modifier you add (whether using one dice or many, a set target number or not) is something players have to keep track of and the more rules/exceptions you accumulate, the slower resolution will be.
- Advancement. Whatever system you use, it seems to me that tabletop games often run for the duration of a campaign/metaplot at a frequency of around once a week. On a MUCK, people can be playing at any hour of any day. If you treat these the same, a MUCK character might advance in a month and a half about as much as a traditional RPG character does in the space of a year. Plus, on a MUCK, you may constantly have new, starting-level characters without loss of experienced ones, creating a huge disparity in power level.
- GM oversight. In a tabletop game, it's usually relatively easy to leave things in the hands of the GM because he/she is there. On a MUCK, mechanics need to be in place to resolve things without, because there may not always be qualified neutral parties/staff available. Similarly, a GM can give more attention to and render judgements more consistently with a handful of players than a team of GMs can over dozens.
Am I wrong, or would each of these games benefit more from design thoughts dedicated to the style of game?