Harley-Davidson motorcycles are more of a brand than a bike, so they're not known for being reliable or comfortable to ride compared to a lot of other bikes. That being said, they're perfectly fine if that's what you want, and you understand that you'll have a higher likelihood of something like a persistent oil leak, or annoying electrical issue.

The local motorcycle school by us uses Yamaha dual sport bikes for taller riders, they're pretty inexpensive compared to other bikes, they can take a beating, and they're pretty easy to buy and sell used.

I have a tall buddy that got a Honda NC700X as his first bike and he's been riding it for years on pretty long road trips. It has an automatic transmission and ABS brakes, so compared to a lot of bikes, it has a surprising amount of safety features.

Of course, get what you like. The old saying is it's better to buy a bike you'll grow out of, then to buy a bike you'll grow into.

If you want both fun and comfort, try a naked bike! You get fairly upright ergonomics, but sporty street performance. Good beginner bikes would include the Yamaha MT-03 and Kawasaki Z400.

If you like crotch rockets, a beginner sport bike is a great choice. They're even sportier but still not very uncomfortable like the 600s. The Yamaha R3 and Kawasaki Ninja 400, or one of the older Ninja EX500's are my beginner recommendations.

If you like the big cruiser V-twins (that's Harley's thing) instead, something like a Honda Shadow 750 or Suzuki Boulevard C50 gets you that experience without paying Harley prices.

Speaking of prices, I highly suggest you buy a used bike as your first, because you may drop it while getting the hang of things and you avoid most of the depreciation of a new bike. Then, you can see what kind of riding you really want to do and upgrade from there!

I started on a 600 🤷‍♂️

They're referring to engine displacement. 400cc and 600cc. You'll find manufacturers tend to make roughly the same engine sizes for different bike types. Like 150cc, 250-300cc, 500cc, 600-700cc, then 1000-1300cc. Since you're starting out, a good idea is to start small like somewhere between a 300-500cc bike. Typically, the larger the displacement, the more power the engine can produce. Practice your skills and get a good foundation for actually controlling the bike at slow and high speeds. A Honda Rebell 500 (cruiser) can go 90mph no problem and is light, nimble, relatively easy to work on, and easy to control at slow speeds since it has a low center of gravity, so it's a bike you can start with and keep for a long time. Honda uses the same 500cc engine in different styles of bikes but with different tuning, like the cbr500 (sport), CB500 (standard), NX500 (dual sport). Eventually if you decide you actually like motorcycles and want to "upgrade," you can get a bigger displacement bike somewhere between 600-1000cc, depending on your needs/interest. What kind of style do you like? Cruiser, sport, standard, etc. You can't go wrong with Honda, Kawasaki, or Yamaha to start off with. They tend to have decent maintenance intervals and are easy to work on.