I ran the rear only brake lever on the right since I broke my left hand. The two smallest digits never felt strong enough when I needed the brake on hard. I now have a dx v brake on the old bmx on the right hand side as the cable runs better to the noodle along the left side of the top tube.
I also have a Haro similar to the one questioned above. Its a team issue from 2009. the cable guides are on the left of the top tube and it came with a carbon/alloy right hand lever. You don’t really need to get used to it. You rip around a bmx track and know that there’s only one brake to scrub off speed with so there’s nothing to actually get into yer head!
The stability of the haro with the 21″ top tube is very confidence inspiring compared to the 20.5″ bike at the track.The Haro alloy frame with chainstays nearly 3 times as deep as the chromoly S&M stays feels like a rocket ship when you put the power down.Fine if you plan on doing a bit of racing or blasting around the track.
Don’t think mountainbikes re: stiff/uncomfy or flexy/more comfortable. It’s not going to come into it! Its a strength/weight/stiffness thing that will be your choice with whatever type of riding you plan to do.. and if you plan on messing about jumping all the time or never leaving a skatepark,then go with a steel frame.If you want to go fast and like the idea of a light bike,then its probably going to be an alloy race bike you’ll end up with,although many riders still race steel (and kick arse on them too)
Don’t think that the bike will always feel completely alien with 20″ wheels. It takes me around 3-4 days to get back into it at the track coming off 26″ wheels so at least give it time. To jump onto one for a few mins,you would think its near impossible.. but stick at it. Like the others have said,consider a cruiser.