From someone who is an absolute beginner to RBAs and who has worked with both the AGA-T2 and RSST in the past week, I would go with the RSST. I has some success with the AGA-T2, but hot spots keep developing and driving me nuts. I received my RSST yesterday and built a nice 1.2 ohm coil right off the bat. One small top leg hot spot that I worked out quickly, and a nice cool vape since then.
Downsides to the RSST (that have already been mentioned): single coil only, plastic tank, air hole is tiny. The air hole is a very quick fix of course, just open it up a little. Some people have had leaks with the RSST, getting juice on the 510 connector. I haven't had any leakage so far.