Joined: Jan 2009
Posts: 44,338
Likes: 6,637
From: New York, NY, and High Falls, NY, USA
Bikes: 1962 Rudge Sports, 1971 Raleigh Super Course, 1971 Raleigh Pro Track, 1974 Raleigh International, 1975 Viscount Fixie, 1982 McLean, 1996 Lemond (Ti), 2002 Burley Zydeco tandem
I've never been to IL, much less know the laws, but the laws usually require a rear, red reflector. Supplementing that is probably legal.
You can get the best of both types by using at least one of each. It's not redundant to have more than one taillight. Any bit of extra protection might help and probably doesn't hurt, except for cost.