That extra front wheel is useful when you need twice the front tire traction, to stop or turn faster, especially when the pavement is slippery.
Also, a 3-wheeler is more stable at slow speeds, when it is common for a beginner to not use the clutch well and drop their bike. If you lean a 2-wheeler over just a little too far at slow speeds, you quickly learn how much heavier it is compared to a bicycle, and it becomes almost impossible to hold up instead of falling over.
A 250cc engine is fine for 1 person on 55 mph speed limit roads, which is what a beginner should limit themselves to. This model is quite expensive, but also quite a bit safer for a beginner or anyone else, especially for someone who wants to ride in below freezing temperatures. The web site states the top speed for the 250cc version is 77 mph:
http://www.piaggiousa.com/scooters.php#/overview/Piaggio%20MP3%20250