I'm grabbing this quote from the general character competitive impressions thread.
From the video it looks like he's using the shortest + fattest combination which people seem to think is the optimal combo since being tall has huge drawbacks and being fat seems to be strictly better than being skinny for some reason.
It would be a shame if default height/width was forced in tournaments resulting in non-optimal and weaker Miis.
There's a discussion to be had regarding the difference between allowing/disallowing items, custom moves, equipment, and varying heights/widths of Mii characters. The former 3 of the 4 have their own threads. I don't see much discussion about the Miis outside of their respective subforums. The community generally accepts items and equipment bans. The latter 2 are more debatable.
Let me start by saying the purpose of disallowing any or some of these is to standardize the competitive game-play experience, and to remove inconsistent game-play interaction, leading to a skillful, suitably complex game where players exhibiting the best skills
we want to test are most likely to win.
The important factors here are the following:
1. Standardized, competitive game-play experience.
2. Consistent game-play behavior and interaction.
3. Used skills are the ones we want to test.
-Items-
Items allow for an extremely volatile and inconsistent game-play experience. They don't allow players to test the character vs. character fighting game skills we simply want to test.
-Equipment-
Equipment values are quantifiable. They are available for testing, and can be displayed before each match. Theoretically speaking, if we were to allow equipment, we could very
generally calculate kill values, combos/strings, and other game-play differences equipment stats alter. However, this extreme of calculation isn't a skill this fighting game community wants to test. Also consider we aren't super computers capable of accurately calculating all of these variable combos/strings, and kill percentages anyways. In short, custom equipment is a quantifiable variable, but it's also so difficult to account for that in practice it makes our game-play experience volatile and inconsistent, and takes away from the other, more important skills we want to test.
-Custom moves-
Custom moves are quantifiable. They can all realistically be learned and adapted to. With a good ruleset, and once the Wii-U version is available (when we can easily unlock all of the custom moves for each Wii-U at tournaments), the competitive game-play experience will be more standardized and consistent. Most of the real debate around custom moves is whether or not we want to test the skill of adapting to a more complex counterpick system than we've ever seen before in SSB. There are some more abstract metagame benefits that come with a more complex counterpick system, but that's a topic for another day.
-Miis-
It's difficult to quantify the Miis height and width variables because they're adjustable on a scale. There are around ~50 different notches on this scale for both height and width. I don't know if each notch has it's own damage, range, speed, and jump height values, or if it's interval based (perhaps 6 intervals, based on the
customization layout), but we know the extremes have different values. Here's a
thread with a lot of the calculation data. The damage value changes are variably insignificant, while range, speed, and jump height change more dramatically. While we can get a general idea of Mii height and width from the in-game pictures and character models, the exact value aren't shown. We have to go back to the Mii customization menu outside of Sm4sh to access this information. ASSUMING the values listed earlier correspond more variably than just the extremes, and even if we specify before each match for example, 20/50 height and 45/50 width, we run into the same consistency problems equipment has when it comes to calculating different interactions.
There is a solution though. There are 9 possible combinations if you use each of the height and width extremes, in order to artificially and somewhat arbitrarily create 9 standardized characters using the Miis. The height/width values and their corresponding stat values are realistically quantifiable, and each variable can be easily displayed visually before each match, within sm4sh. But is it appropriate to have players learn each of the heights and widths and calculate for each? Is 9 variations of 3 different Miis (27 in total) too much? That's a lot more characters to learn. On the other hand, perhaps using the default Mii height/width is best.