We just returned from Sicily, driving for 10 days. We took many back roads, drove into large cities, and didn't get lost or have any accidents! Here's my advice on maps and directions..
Long Distance / Country Driving
We took a GPS app which we never used, and both the Italian touring club 1:200,000 Sicily (map 14) and the Michelin 1:200,000 Sicilia (map 365).
Although the touring club map was highly recommended, and appears clearer, with larger print and bigger roads, we quickly put it away and used only the Michelin map. Turns out the reason the Michelin map is a little harder to read (smaller print, looks busier) is because it has twice the roads on it! We would not have gotten most places we went with only the touring club map. Driving anywhere in the countryside was easy with the Michelin map - the smallest of roads were accurately shown, and the width of the line reflected the relative width of the roads. Road numbers are rarely shown on signs, so directions (such as goggle maps) using road numbers are useless. You need to follow signs for where the road ends, not where you are going - a good paper map makes this easy. We had no problems.
City / Town Driving
Again, street signs are not dependable - sometimes they are there, many times they aren't. Directional signs to museums, attractions, and hotels are also hit and miss. I took every Sicily book there was out of the library before we left home, and photocopied ALL of the city and town maps. I also had several guides books with me (I cut them up and take only the relevant chapter with me each day), so I had those maps too. We studied the maps before heading out each day, and were able to follow the street signs easily when they did exist, and use landmarks (churches and parks) and make informed guesses about which way to go when there were no signs. Having maps, however crude, of towns is particularly important when you encounter the inevitable one-way street maze, OR street closures - which are common. I can't imagine how a GPS would help in these situations.
Driving in Sicily certainly isn't for the meek or faint of heart, but it can be fun and safe with a little preplanning!