In terms of grading, which is a criteria you have listed, Georgia Tech is definitely a harder school. They are known for slight grade deflation throughout various forums. But, as an overall school, Georgia Tech seems to be more prestigious and well-known when compared to UIUC. UIUC has a great Computer Science department, but Georgia Tech (in addition to having a great Computer Science department) has many other great STEM majors allowing for a lot of interdisciplinary research/projects. Also, the average student at Georgia Tech seems to be a lot smarter than that of UIUC (primarily since its a more competitive school). As such, Georgia Tech has a far more academic vibe to it (kind of like UCB, CMU). Plus, for the only undergraduate ranking of CS + EE on USNews, Georgia Tech is ranked 4th and tied with Stanford; whereas, UIUC is at 6th.