Both circuits are man-made, carved out of virgin scrubland in recent years, and both provide entertaining venues for Formula One races, if not for Grand Prix races. By modern standards the Estoril circuit is medium-fast, with a lap record of 122.7 mph, while the Jerez circuit is slow, with a lap record of 108.5 mph.
Of the two, my preference is for the Portuguese circuit, which has a fast, slightly downhill straight past the pits, entered from a fast right-hander. In qualifying the front-runners were touching 208 mph before slamming on the brakes for a fast downhill right-hand sweep. In the centre of the Autodromo the course also runs downhill to a double-left hand bend, where some pretty demon overtaking goes on, and after another straight followed by a tight, falling-away right-hand bend, the circuit climbs upwards again through some twists and turns back onto the top straight.
In contrast the Jerez Autodromo is virtually flat, rather mickey-mouse, and full of twists and turns, with the only real straight being past the pits, entered by a slow hairpin and ending on a slight up-gradient and a slow right-hand bend. If you view the circuit from the top of the control tower at the start/finish line it has the appearance of an over-size table-top slot-car track. You can see it at seven different points, each going in a different direction —very confusing!