Great question — both are solid upgrades over standard economy, but they offer different benefits:

• Exit row: best for maximum legroom. You’ll get significantly more space to stretch out. The trade-offs are slightly narrower seats (tray table in the armrest), fixed armrests, and no personal items at your feet during takeoff and landing.
• Rows 3–5 (LATAM+): a more balanced upgrade — extra legroom (though less than exit rows), standard seat width/comfort, priority boarding, and quicker exit on arrival.

Bottom line:

• If your priority is maximum space → go exit row
• If you prefer overall comfort and convenience → rows 3–5

For relatively short flights like GIG–FOR or FOR–GRU, rows 3–5 are often the more practical choice.

One more angle to consider: the price difference might be marginal, it can be worth checking an upgrade to Premium Economy. You’ll get a blocked middle seat, more personal space, and an overall quieter, more comfortable experience — a noticeable step up from either option.