i don't know much about audition, but i use reaper alongside protools, and being proficient in both now, protools' elastic audio is literally the ONLY feature preventing me from being full-time reaper. As it is now, i'm tracking/editing in protools then bouncing/moving the mixes over to Reaper to mix. it seems to be alot more stable. in windows, atleast.
elastic audio aside, reaper is EXTREMELY powerful with editing, and becoming more-so all the time. you can even sortof "fake" elastic audio in reaper, but it requires making splits. a "warp marker" oriented time edit feature in reaper, i believe, is currently in development. and if that drops and works well, then...well, that'd be huge.