Shueisha / Manga (source: Daizenshuu 2)
[Remember, it's only one series, so no DBZ!]
DragonBall; 15 arcs
- Search for the Dragonballs (chapters 001-023)
- Training with Kame-sennin (chapters 024-031)
- 21st Tenkaichi Budoukai (chapters 032-054)
- Red Ribbon Army (chapters 055-096)
- Uranai Baba (chapters 097-112)
- 22nd Tenkaichi Budoukai (chapters 113-134)
- Piccolo Daimao (chapters 135-165)
- 23rd Tenkaichi Budoukai (chapters 166-194)
- Saiyan (chapters 195-242)
- Freeza (chapters 243-337)
- Artificial Human (chapters 338-356)
- Cell (chapters 357-420)
- High School (chapters 421-429)
- 25th Tenkaichi Budoukai (chapters 430-445)
- Majin Buu (chapters 446-519)
Shueisha / Manga (sources: DB Landmark and Forever)
[These guidebooks use essentially the same divisions as Daizenshuu 2, but are a tad different, so be sure to look closely.]
DragonBall; 15 arcs
- Search for the Dragonballs (chapters 001-014)
- Training with Kame-sennin (chapters 015-032)
- 21st Tenkaichi Budoukai (chapters 033-054)
- Red Ribbon Army (chapters 055-096)
- Uranai Baba (chapters 097-111)
- 22nd Tenkaichi Budoukai (chapters 112-134)
- Piccolo Daimao (chapters 135-164)
- 23rd Tenkaichi Budoukai (chapters 165-194)
- Saiyan (chapters 195-243)
- Freeza (chapters 244-329)
- Artificial Human (chapters 330-357)
- Cell (chapters 358-420)
- High School (chapters 421-429)
- 25th Tenkaichi Budoukai (chapters 430-444)
- Majin Buu (chapters 445-519)
Shueisha / Anime (sources: Daizenshuu 3, 5, & 10)
[The TV Animation daizenshuu split up each arc into smaller acts, but I'm not going to list all those.]
DragonBall; 5 arcs
- Son Gokou (episodes 001-028; 11 acts)
- Red Ribbon Army (episodes 029-068; 10 acts)
- 22nd Tenkaichi Budoukai (episodes 069-101; 9 acts)
- Piccolo Daimao (episodes 102-132; 7 acts)
- 23rd Tenkaichi Budoukai (episodes 133-153; 7 acts)
- Attack of the Saiyan (episodes 001-035; 10 acts)
- Battle on Planet Namek (episodes 036-074; 11 acts)
- Terrible Emperor Freeza (episodes 075-107; 10 acts)
- Fight with Garlic Jr. (episodes 108-125; 7 acts)
- Android No. 16~20 (episodes 126-147; 7 acts)
- Over the Super Saiyan (episodes 148-165; 7 acts)
- Beginning of the Cell Games (episodes 166-194; 8 acts)
- Anoyoichi Budoukai (episodes 195-219; 8 acts)
- Majin Boo Returns (episodes 220-237; 5 acts)
- Appearance of the Super Saiyan III (episodes 238-254; 7 acts)
- The Final Fighter, Vegetto (episodes 255-268; 5 acts)
- The Final Battle (episodes 269-291; 6 acts)
- Nothing about the GT story arcs has ever been officially classified by Shueisha. The GT Perfect Files don't organize the episodes by arc, but by the location of each episode.
Toei Animation (source: Official Websites)
DragonBall; 6 arcs
- Encounter with Bulma (episodes 001-013)
- 21st Tenkaichi Budoukai (episodes 014-028)
- The Search for the Four-Star-Ball (episodes 029-068)
- 22nd Tenkaichi Budoukai (episodes 069-101)
- Daimao's Revival (episodes 102-132)
- 23rd Tenkaichi Budoukai (episodes 133-153)
- Saiyan (episodes 001-035)
- Freeza (episodes 36-117)
- Cell (episodes 118-199)
- Majin Buu (episodes 200-291)
- Dark Dragonballs (episodes 001-022)
- Baby (episodes 023-040)
- Super 17 (episodes 041-047)
- Evil Dragon (episodes 048-064)
Toei Animation (source: Dragon Box)
[Just like Shueisha, you'll note that Toei isn't all that consistent either.]
DragonBall; 11 arcs
- Goku and Bulma (001-013)
- Kame-sen Training (014-018)
- 21st Tenkaichi Budoukai (019-029)
- Red Ribbon (030-068)
- Uranai Baba (069-078)
- Training on the Road (079-083)
- 22nd Tenkaichi Budoukai (084-101)
- Piccolo Daimao (102-123)
- Heavenly Training (124-132)
- 23rd Tenkaichi Budoukai (133-148)
- The Wedding Dress in Flames (149-153)
- Saiyan (episodes 001-035)
- Namek (episodes 036-074)
- Freeza (episodes 075-107)
- Garlic Jr. (episode 108-117)
- Artificial Human (episodes 118-147)
- Cell (episodes 148-194)
- Ano Yo-ichi Budoukai (195-199)
- High School (episodes 200-209)
- Buu (episodes 210-291)
- Searching Space (001-022)
- Super Baby (023-041)
- Super No. 17 (042-047)
- Evil Dragon (048-064)
You'll note that on Kanzentai we (I, mostly) use a mix of all of them in some way. I personally split the series up into main arcs, and then divide some of those into smaller sub-arcs. That said, I have been debating lately about breaking up the Z story arcs a little more on the site, just so the pages aren't quite so long and will load faster. I know the Japanese Wikipedia DragonBall pages do split things up fairly similar to our current pages. Basically, everyone splits the series' up a little differently, pertaining to their specific tastes. You'll also note that FUNimation even splits the series up differently than the Japanese companies, and of course they call them sagas, which has always bothered me. I know that may sound "elitist" of me, but it's just a fact. The definition of a saga is "A long detailed report" which is typically a narrative. I'd say neither really applies to DragonBall. Whereas the definition of a story arc is "An extended or continuing storyline in episodic storytelling media". I guess it's just one of those things that annoys me, although not as much as making up seasons that don't exist.
Anyway, as long as someone has the Freeza arc ending at a logical point, like right after Namek explodes (episode 107) or sometime around Trunks arrival (episode 125), I don't really see a problem with it. It's one of those funny arcs that falls into a transition from one arc to the other arc, but is still an arc of its own merit. That's why it's so hard to definitively place it in one or the other. However, it seems that the consensus is that the Trunks arc fits better in the Artificial Human arc, especially in the anime. In the manga it's much easier to have it in the Freeza arc, since the Garlic Jr. arc doesn't interfere.
I love how every time there's a discussion about the division of story arcs, I update this list with another source and make it even longer.

