in a full ring cash game against bad players, TAG is always more profitable, since bad players never fold. In a game with a lot of good players, LAG might be the better option.
Why is that? What if you have a huge edge postflop?
The may never fold but then its up to you to go all the way with top pair when you know that the villain has something worse
Changing up play and strategy is what makes a player good. Adjusting your style to the table is critical to your success. I can be TAG OR LAG based on those around me. Once i settle on my play, i usually dont change much duri ng a session until the players around me change.
You can not play one or the other mode only. You have to adapt as quickly as possible to table the style you are playing, especially in major tournaments. I would say you should play conservatively pre-flop and post-flop aggressively.