yes, you will get much better bang for your buck in research with agriculture than you will with commercial. Some people say its not good cuz you`re dependent on the market, but its like if you sell at least at 4 you`ll always make more than a commercial terran with equivalent research and land. Plus, when you cluster, you get additional bonuses to agriculture production (esp with c3).
So really, it`s a more a question of, would you rather make 1,000,000 a turn, or would you rather make anywhere between 1,000,000 - 10,000,000 a turn depending on food prices? Cuz food always sells at least at 4 or 5 per unit, unless you`re on a crazy server like RT where on some days people can produce so much food that it sells cheaper than CGs.