Well, i'm gonna be working on the assumption first that you are a f2p, which means no strong support ninjas yet like edo itachi, fusion kisame, etc. This also means that you either want to get a pos 1 'main' ninja for your 20k cpns.

Now, lets go through and 'eliminate' bad choices.

SSN Kakashi - terrible choice for f2p's 20k cpns, has pathetic damage, 3 round cooldown. Its exclusively a support ninja.

Sasuke "Rinne Sharingan" - his main problem is low damage output on his mystery and no interrupt ability. He's a good 2nd-dmg/support ninja for ppl who have strong pos 1 ninjas already, but not for a f2p.

Hiruzen "Edo tensei" - This is a ninja that basically has one use; as a Sage World Battlefield kill-streaker. This also means you need to have a pretty high power to use him well. If you're facing players 30k+ lower power than you in Sage, then this is a good option to get high streaks and get adv refines. But otherwise, he's not a strong ninja, especially in 1v1 matches against similar power.

Bee "8 tails chakra" - he's 'alright', but compared to 6 paths naruto, Kbee is basically inferior in almost all forms.

Minato "Edo tensei" - he's pretty strong, but ONLY if you are faster. If you're slower (for f2p's, this is usually the case), this is a really bad ninja to have.

Tobirama 'Edo Tensei' - another support ninja, one usually only used with edo hiruzen after u have edo hashirama. Not smth a f2p needs.

Now this brings us to the last two ninja, which I think are your only two worthwhile options

- Konan "AoG" - Has incredible 9+ ninja damage (especially with chakra), hits through dodge, cooldown reduction. If you have fusion kisame or regular madara, this is a great ninja to use in both GNW and for 1v1 matches in sage. Mostly immune to chases. Her downside is that mystery doesn't interrupt, and she alone isn't immune.

- Naruto "6 paths" - Has rather poor mystery damage but good standard damage. Interrupts 9+ ninjas. Cooldown reduction. Chase removes buffs. Has leech. Has dodge. Etc etc... 6p naruto is the most broken ninja in the game, and most likely your best choice as he does not require any support ninjas. His only downsides are that your matches will take a long time even when you are much stronger (so suboptimal for Sage), and his mystery doesn't hit through dodge (so can't interrupt minato, shisui, etc).

Note that of the ninjas we are going to receive (based on CN ninjas), Grudge Mode Kakuzu's skill breakthroughs are more powerful than 6 paths Naruto. So in the long run, Kakuzu is better than 6 paths naruto or AGK. However, we DON'T KNOW if we're gonna get kakuzu's SB's at all, or if he's going to be nerfed. So atm, 6p naruto and AGK are your best bets most likely.

I should also note that of the 'good ninjas' that you listed, you missed out a few. Notably, Edo Tensei Itachi and 5 Kage Madara.

If you're a f2p, one option u c*e is water main pos 1 shark bomb.

For this team, 5k madara and edo tensei itachi are both great support ninjas