There are a few factors to consider here: as already stated, if L1, R1 makes for easier sideshifts, then on Venom and Flash, stick with L1, R1 because you really won't brake much on those speeds. Likewise since airbraking is more common on higher speeds, then the ability to "feel out" the turn by using the digital L2, R2 provides optimal lines.

I personally got used to L2, R2, and I use that for every event. For me, it isn't bad sideshifting with them, and the ability to control airbrakes really helps when flying Icaras, which I always do, if I came to a full stop on each airbrake using L1 & R1, I would lose out to Feisars, Harimau, and AG systems on tighter turns.

What this really all boils down to is what you are used to. But I personally think that L2 R2 has a slight advantage overall.