Would another factor be which species of plants are involved? You can have low light/easy plants in a high light excel only tank and they will grow very well, but throw in some high demanding plants in the same situation and I don't believe they would grow very well (compared to a high light +
CO2 tank).
High/Med/Low tech
IMO is exactly that, an opinion. That being said, the "general" guideline I am familiar with is:
high tech: high light,
CO2 strict fert doing.
med. tech: med/high light, excel and fert dosing.
low tech: low/med light, some fert dosing.