I would stay away from the 600cc Honda Shadow VLX cruiser for a beginner- they were last made in 2007 and the clutch is a little tricky for a beginner (I have one I bought new in 2002). Also, the 1999 to 2007 single carb model needs rejetting to have decent takeoff power- a beginner stalls it easily when taking off, the steering is heavy at slow speeds for the more chopper looking forks, and the stock seat is terrible.
Air cooled engines except maybe a scooter get hot at stoplights on a hot summer day and the hot air goes up toward you, and they have less power at 75 mph compared to water cooled engines. This includes the 500cc Buell Blast, the 500cc Suzuki, the 650cc Suzuki S40, and the 500cc Royal Enfield.
For a beginner, I would look at the 250cc Suzuki cruiser with fuel injection, a 250cc Kawasaki Ninja, the 500cc Kawasaki Ninja or Vulcan, a 250cc to 500cc Kymco scooter, a 250cc to 500cc Yamaha scooter, or a 500cc Piaggio scooter. You can get by with more weight for a scooter, because the weight is lower than for a motorcycle, and not having to use a manual clutch makes it easier at parking lot speeds. The only 250cc that does well at 75 mph with no passenger is the 250cc Ninja.