Their current sales pitch is that they're not infantry. I've heard their seniors say it. Won't stop them sending people to Brecon at career stages commensurate with equivalent ranks in the Army.
As to being above and beyond infantry in terms of training, they definitely do so different stuff. However, I understand at a recent, possibly the last, visit of the Joint Service Job Evaluation Team, who assess trades for pay banding, they gave the RAF Regiment less 'points' than both Army inf and Royal Marines.
Again, that was stated in public forum by one of their seniors.