When comparing Monsters & Magic vs GRIN, the Slant community recommends GRIN for most people. In the question“What are the best tabletop RPGs?” GRIN is ranked 36th while Monsters & Magic is ranked 42nd. The most important reason people chose GRIN is:
GRIN uses a a standard deck of playing cards instead of dice.
Ranked in these QuestionsQuestion Ranking
Pros
Pro The Effect Engine
The game uses a single core mechanic, which is flexible enough to cover a wide variety of situations. This helps GMs immensely when characters want to do things that aren't already covered in the system.
The mechanic itself works thusly: all rolls are 3d6 + modifiers minus difficulty. The result is how many effect points the player can apply to the action -- or, if negative, how many consequence points their opponent can apply to a reaction. Dealing damage is one use of effect points, but there's a limit on how much can be dealt at once, so additional effects (e.g. distracting, disarming, unmounting, etc.) see constant play instead of only being used rarely or by super-specialists. This also means failure is interesting, since it results in consequences!
This mechanic is used to do everything, and the game essentially consists of nothing but examples of how to use it.
Pro Interesting combat
Attacks generate effect points, which you spend to do things to your opponent. However, the amount of damage you can do is limited, which forces players to do other things... and the effect system is broad enough that these can be things like cutting off a carrion crawler's tentacles, knocking an opponent's sword out of their hand, and so on. Failures on attack generate consequence points as well, which your opponent can use to do things to you.
Pro Mental defense and hit points
Characters have a "Mental Defense" score and "Mental Hit Points". These are used to help provide a unified system for handling social encounters and mental attacks via magic.
Pro Zero dice required
GRIN uses a a standard deck of playing cards instead of dice.
Pro Narrative focus
With no intrusive dice or math players can focus on the story, with every action being resolved by the simple draw of a card.
Pro Creates excellent tension
GRIN uses a a standard deck of playing cards to create a fast paced and deadly feel that evokes modern horror films. One of the best horror games made, its ideal for Halloween or horror movie nights.
Pro Its great for single session games
Like any horror film, characters will die. Grin lends itself to deadly games and rally shines with 4-6 players and narrative arcs lasting 3-4 hours.
Pro Easy to improvise
With the intrinsic arc of a classic horror narrative built into the core mechanic, Grin can be an intuitive framework for improvised play.
Pro Unique mechanic
In true horror movie style, death becomes increasingly likely as the game's story moves irrevocably forward.
Pro Easy to pick up
The game has just one page of rules. It can be explained in a minute -- even to people who have no rpg experience.
Cons
Con Not currently available in print
Is only available in PDF.
Con Few monsters & spells provided
The included rules have only about 20 monsters and 1st and 2nd-level spells. Third party publishers have supplements that provide more, or you can use ones from old D&D.
Con Can be seen as too simple for some
Because each encounter has just two possible outcomes - success or death - there's little wiggle room in terms of roleplaying.