Im just doing a little bit of comparison and here what I found :

Chapter Number for Murata version: | Chapter number in Original Webcomic: | Chapter number at http://tonarinoyj.jp/ manga/onepanman/:
17th Punch: Sparring | 17 | 17 &18
18th Punch: Business Activity | 18 | 19
19th Punch: No Time For This | 19 | 20
20th Punch: Rumor | - (None) | 21&22
21st Punch: Giant Meteor | 20,21&22 | 23,24,25&26
22nd Punch: Voices | 22&23 | 27

Damn, I just cant resist the urge for going on ahead, and so I read (just looking at pictures) chapter 24-31 from the original webcomic from ONE, and now I already know whats gonna happen. I think the new arc end at chapter 31 (thats why I stop) but I dont know how many chapter it would be for the other version. So many fighting, so many heroes come and gone, so many tension for what to come...