I moved the topic to Strategy and Tactics.
To answer your question, while the bonuses are the same, the clans have different style of play and use in game modes.
For instance, La Junta are a very strong clan in mono because of the heavy amount of Support:Ability cards. FPC however, does not have as many and play much better in a half deck but in return have generally a higher power compared to La Junta.
This can be seen with Piranas and Nightmare as well. Piranas have many pill manipulation cards making this a very effective if done well but difficult way to play them. Furthermore, Piranas compared to Nightmare have slightly higher power but lower damage meaning that it is much more essential to win most if not all the rounds. Nightmare on the other hand can turn the game around with one or two rounds won because of a higher damage output and a lot of + life cards. However, as I stated before, their power is slightly lower than Piranas.
My take on the clans (these are my opinion):
All Stars Fang Pi Clang Ulu Watu: Pressure with high power
Bangers Sentinel: Pressure with strong power and damage (especially if unopposed)
Freaks Jungo Sakrohm Nightmare: Life control
Junkz Piranas: Pillz control
GHEIST La Junta: Pressure with high damage
Frozn Huracan: Round control
Pussycats Vortex: Counterattack
Roots Skeelz: Pressure with ability
Montana Rescue Uppers: Pressure with attack
My take on the "double" clans:
Fang Pi Clang, Roots, and Ulu Watu have higher base power than Bangers, GHEIST, and La Junta. However, Bangers, GHEIST, and La Junta are heavier in base damage.
Nightmare have life abilities, while Piranas have pill abilities
IMO, Sentinel have either good power or damage while getting strong power and damage with their abilities, while Junkz is more well-rounded.
Some clans fits different play style, also some clans excel in different areas and stars. there are some clans that can use all of their 2* and 3* but still good, some other better in their 4* and 5* department.
the post above give a good start to understand differences in clans
to be honest, now the differences is a little bit unclear, each clans has more and more cards that their opposite has
before fang pi is the low power high damage clan, and La Junta is high power lower damage, now it is the other way around..
fang pi: pure power and damage, kinda low ish damage on their 2-4* cards (compared to la junta's), not much of variety in ability very straight forward clan (something that I really like about them). they do have some small amount of trick on the sleeve though such as Kusuri and Tsubame
2*: Chan, Dao Wang, Kusuri, Marlysa Cr, Yumi, Muntendon (to some extend Sakazuki and Unagi)
3*: Nakata, Sayura, Shifou, Ralph, Zhu Tang, Yu Mei
4*: Fei, Futoshi Ld, Shizawa, Heitachi, Zinfrid
5*: Yoshida, Tsubame, Kerozinn Cr, Sung Tsu, Kuei, Hattori
La Junta: a little bit less power (but still good) but more damage (either pure or in their ability), more variety in ability, and has support (good in mono)
2*: Thormund, Dean, Wardog, Victoria, Sabia, (and Winston in some case)
3*: Trish, Jane Ramba Cr, Laura, Milena, Nahomi, Archibald, Bruce
4*: Gatline, Bryan, Brianna, Arnie, Isatis
5*: emeth, Dugan, ed12, General Cr, Ray, Pilzken, Raven
Rescue vs Montana
Similarities: Both clans have low base power (favor 5-7 instead 6-. Their bonus, however makes up for their low power by forcing their opponents to pill. However, this bonus reliance makes them prone to SoB
Rescue: I like to think of Rescue as one of the most versatile clans. The plethora of life gain, damage manipulation, attack manipulation, power manipulation, and high damage cards makes most Rescue decks flexible enough to handle most situations. Their bonus allows them to beat most bluffs and create walls out of vertically any card.
However, the Rescue clan is highly susceptible to both SoA and SoB (although they have Glosh and Beverly to make up for SoA). Another flaw is that their SoA and SoB cards are almost constantly on the ban list, making them susceptible to being out manipulated by opposing abilities. And of course, Rescue cannot be half decked without losing their bonus's effectiveness.
Montana: I have had less experience with the Montana so this is less accurate then Rescue. It seems to me that Montana favors high damage more than Rescue. As a result, the Montana favor the life gap win then the Rescue (who prefer life manipulation). They acheive this through higher base stats then Rescue, makeing them less prone to SoA. Unlike Rescue, the Montana bonus allows them to be half decked, increasing their effectiveness with other clans. However, the min of 8 forces most Montana to pill twice to reach their min, forcing pills.