The big "gimmick" of Sega Rally is the track deformation and how it affects each lap of each race more than you ever could have imagined such a relatively small element could. Blast through a huge puddle and you'll leave a muddy trail in your wake until the water evaporates off your tires, making the track that much more slippery for when you next hit that section. Carve through deep snow and you'll uncover the hard gravel surface below. Take a corner hard on tarmac and you'll lay down steaming rubber which will make it easier to take the same corner again at greater speeds. Basically, this element changes each course every single lap, making Sega Rally a constantly evolving challenge that forces you to look out for alterations in the track surfaces that can shave fractions off your best lap times and means the difference between victory and cruel defeat.
Every course mixes up the road surfaces devilishly well and even though there aren't many in the game, this means that you can really give each of them your full attention and learn them well - far more so than if there were 50+ tracks as so many games love to brag. It all harks back to the good old days of gaming where tracks would get carved into your brain, making the real goal to tame each one and learn when to stay on the gas and when to slam the brakes.
But with each car being so different from the last, it'll take you a while to find one that works with your style of play. Some favour top-end speed over cornering, while others allow you to tap the handbrake button and cruise around all but the most angular of corners at insane speed. You're even given the option to take either off-road or stock tires, the former giving better traction on the frequent surface changes while the latter gives you better acceleration and top speed.