That's rather difficult to answer. Because of their design, some require more button pressing than others. Meanwhile, others will require more reads and such.
![Bowser :4bowser: :4bowser:](data:image/gif;base64,R0lGODlhAQABAIAAAAAAAP///yH5BAEAAAAALAAAAAABAAEAAAIBRAA7)
is not an execution heavy character, but he requires thought out strategy to do well. Meanwhile, you have
![Greninja :4greninja: :4greninja:](data:image/gif;base64,R0lGODlhAQABAIAAAAAAAP///yH5BAEAAAAALAAAAAABAAEAAAIBRAA7)
who is execution heavy, but does need as well thought out of a strategy to do well. This isn't to say
![Greninja :4greninja: :4greninja:](data:image/gif;base64,R0lGODlhAQABAIAAAAAAAP///yH5BAEAAAAALAAAAAABAAEAAAIBRAA7)
can just derp around. Rather, his strategies are more short term than long term.
There are lot of factors to consider that makes this a difficult question. It depends on move safety, mobility, power, weight, etc. It's best to look at it from a playstyle point of view to get a good idea.
Rushdown (i.e.
![Roy :4feroy: :4feroy:](data:image/gif;base64,R0lGODlhAQABAIAAAAAAAP///yH5BAEAAAAALAAAAAABAAEAAAIBRAA7)
![Sheik :4sheik: :4sheik:](data:image/gif;base64,R0lGODlhAQABAIAAAAAAAP///yH5BAEAAAAALAAAAAABAAEAAAIBRAA7)
) - More execution heavy than strategy heavy. Their moves can be very safe and have a lot of mobility, but their strategies revolve around getting in - some easier than others.
Zoners (i.e.
![Link :4link: :4link:](data:image/gif;base64,R0lGODlhAQABAIAAAAAAAP///yH5BAEAAAAALAAAAAABAAEAAAIBRAA7)
![Samus :4samus: :4samus:](data:image/gif;base64,R0lGODlhAQABAIAAAAAAAP///yH5BAEAAAAALAAAAAABAAEAAAIBRAA7)
![Duck Hunt :4duckhunt: :4duckhunt:](data:image/gif;base64,R0lGODlhAQABAIAAAAAAAP///yH5BAEAAAAALAAAAAABAAEAAAIBRAA7)
![Zelda :4zelda: :4zelda:](data:image/gif;base64,R0lGODlhAQABAIAAAAAAAP///yH5BAEAAAAALAAAAAABAAEAAAIBRAA7)
![Villager Male :4villager: :4villager:](data:image/gif;base64,R0lGODlhAQABAIAAAAAAAP///yH5BAEAAAAALAAAAAABAAEAAAIBRAA7)
) - In this game, they're not particularly execution heavy, but they need good knowledge of their toolkit and can apply their techniques in diverse ways.
Grapplers/Tanks (i.e.
![Bowser :4bowser: :4bowser:](data:image/gif;base64,R0lGODlhAQABAIAAAAAAAP///yH5BAEAAAAALAAAAAABAAEAAAIBRAA7)
![Ganondorf :4ganondorf: :4ganondorf:](data:image/gif;base64,R0lGODlhAQABAIAAAAAAAP///yH5BAEAAAAALAAAAAABAAEAAAIBRAA7)
![Donkey Kong :4dk: :4dk:](data:image/gif;base64,R0lGODlhAQABAIAAAAAAAP///yH5BAEAAAAALAAAAAABAAEAAAIBRAA7)
![King Dedede :4dedede: :4dedede:](data:image/gif;base64,R0lGODlhAQABAIAAAAAAAP///yH5BAEAAAAALAAAAAABAAEAAAIBRAA7)
![Charizard :4charizard: :4charizard:](data:image/gif;base64,R0lGODlhAQABAIAAAAAAAP///yH5BAEAAAAALAAAAAABAAEAAAIBRAA7)
) - Not execution heavy because their attacks can do 2-3x as much as other characters. They are very strategy dependent and require a deep understanding of fundamentals, giving them one of the higher learning curves.
Footsies (i.e.
![Ryu :4ryu: :4ryu:](data:image/gif;base64,R0lGODlhAQABAIAAAAAAAP///yH5BAEAAAAALAAAAAABAAEAAAIBRAA7)
![Marth :4marth: :4marth:](data:image/gif;base64,R0lGODlhAQABAIAAAAAAAP///yH5BAEAAAAALAAAAAABAAEAAAIBRAA7)
![Mario :4mario: :4mario:](data:image/gif;base64,R0lGODlhAQABAIAAAAAAAP///yH5BAEAAAAALAAAAAABAAEAAAIBRAA7)
) - Middle of the road charactrs in terms of range, power, execution, and strategy. Excellent for teaching beginners.
Speedsters - (i.e.
![Fox :4fox: :4fox:](data:image/gif;base64,R0lGODlhAQABAIAAAAAAAP///yH5BAEAAAAALAAAAAABAAEAAAIBRAA7)
![Pikachu :4pikachu: :4pikachu:](data:image/gif;base64,R0lGODlhAQABAIAAAAAAAP///yH5BAEAAAAALAAAAAABAAEAAAIBRAA7)
![Wario :4wario: :4wario:](data:image/gif;base64,R0lGODlhAQABAIAAAAAAAP///yH5BAEAAAAALAAAAAABAAEAAAIBRAA7)
![Sonic :4sonic: :4sonic:](data:image/gif;base64,R0lGODlhAQABAIAAAAAAAP///yH5BAEAAAAALAAAAAABAAEAAAIBRAA7)
) - Excellent speed, but may require zoning, rushdown, and footsies as part of their strategy and execution.