1) The transmission failure you're concerned about here is shock loading. In other words, your initial torque thrown at each gear as you shift into it.
2) The RA gears are a very similar design to the stock gears. They're stronger but have the same failure tendencies.
How DO you want to drive and what power levels WILL the car be at? Without good answers to those, it's hard to tell you what to do.
Generally, RA gears are for stage 2 or small turbo upgraded cars. They then provide about stock durability in a higher powered car. If you want to make big power, they are very breakable. You're better off in the long run buying something stronger like a PPG setup.
2015 STi: Still Stock
04 STi, 04 WRX: SOLD