From year 1 to year 2, Company 1 added 6 employees (went from 6 to 12).
From year 1 to year 2, Company 2 multiplied the number of employees by 6 (went from 6 to 36).
The appropriate description is the last one ...
... company 2 because it is multiplying its number of employees by six each year while company 1 is adding 6 employees each year
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Multiplying by 6 each year causes the numbers to increase much faster (as you can tell by looking at the tables). Since the investment choice depends on larger numbers of employees, Company 2 is the better choice.