When comparing Petzl Reverso 4 vs Edelrid Mega Jul, the Slant community recommends Petzl Reverso 4 for most people. In the question“What are the best belay devices for rock climbing?” Petzl Reverso 4 is ranked 6th while Edelrid Mega Jul is ranked 12th. The most important reason people chose Petzl Reverso 4 is:
Using it as a tuber/rappelling device, belay or guide belay is always used in the same direction (carabiner from bottom). This also allows to switch to back to climbing in an abseil situation.
Specs
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Pros
Pro Use as tuber and guide mode in same direction
Using it as a tuber/rappelling device, belay or guide belay is always used in the same direction (carabiner from bottom). This also allows to switch to back to climbing in an abseil situation.
Pro Asymmetrical design
With one side providing significantly more friction.
Pro Auto-locks even if brake end of rope is not held
In case belayer is disabled, etc.
Pro Lightweight
Pro Passive assisted braking
Pro Three rappelling modes
Can be used in 2 orientations, for rappelling with or without brake assist, and can add a carabiner for lever action, making it similar to a GriGri.
Cons
Con No assisted braking
Con Behavior is highly dependent on rope diameter and type
"stiff ropes feed very poorly. 9.7 and above ropes feed poorly for lead belay. Soft and supple skinny ropes don't lock as abruptly. Half ropes in the 8-8.5 range DO NOT LOCK FULLY with the proper edelrid strike biner" https://www.reddit.com/r/climbing/comments/6aoipn/nonjerky_method_for_rapping_with_mega_jul_in/dhh1vvx/
Con Guide mode with thin ropes can flip and disable auto-blocking
Video demonstration with stories of it happening in the comments: https://www.youtube.com/watch?v=385cP_FYNEs