Rb has its problems which can get expensive to fix, but done right its reliable, more reliable than sr20det (i've seen more sr blown mostly due to valvetrain issues), although generally not as reliable as a 1/2jz. Here's a link to a video of my friends rb25det A31 Cefiro doing an 11 lap race of a 2,3 mile circuit, no heat problem with it, and has been reliable ever since he swapped in the rb25det to replace his blown rb20det (only blown because of over nitroused to help spool a large turbo, pre nitroused the rb20det survives 4 years of abuse of 8000rpm drift runs, drag racing, etc) :
Super Touring - Mimo Cefiro - Final Battle 2012 - YouTube
Over 20 minutes of racing is quite reliable no?
Nose heavy? seems not a problem from the video, you can fine tune the car or adjust your driving style to adapt to sr20det or rb/jz powered,