Which is better for performance when sending emails - Canvas or Content

Continuing the discussion from Compose column, with a link to reference ThisRow:

I have a question regarding the email template approach.

Which is better for performance when having lots of rows in a table:
a) to have a canvas column with the composed template for all rows and in the Send email button the Format(),
b) to have the email text in the Content field in the Send email button. In this case, the button would be disabled for most of the rows

Or maybe c)

What would be your recommendation?