I have spent time doing both wet and dry jelqing and can say without doubt dry has created most gains.
I would add a rider however. I believe the inexperienced PE’er should include only wet jelqing in their routine until - as someone else has hinted at lately- a conditioning has had time to occur. I mean by that that it is unrealistic to begin a routine and expect results immediately. You have to go through a hardening up experience before launching out into a more demanding set of exercises. At that stage dry jelquing becomes an option.
I am a very very senior PE’er and do not wish to give too many details away but I can say that for over two years when my routine was exclusively based around wet jelqing my gains were less than half an inch. I have now gone from five to seven inches fully erect and the greater gains have come within 9 months since the dry method was introduced.
Of course, it could be argued that it took a large slice of the two years to achieve the platform for speedier increases to occur.