Because it comes up relatively often, I thought I’d put up a poll to gauge what people feel are the “best” multi-colored planeswalkers.
“Best” is obviously a somewhat subjective measuring yardstick but if you consider:
What planeswalker do YOU consider the Best?
Corrected spelling in the poll 
// Alve
EDIT - Thanks Alve… I was still waking up when I posted this.
Aj has decent manna gen across the board and amazing built in control. Also the red / white synergy is the best of what we have right now. He’s not my favorite, but he’s definitely the most versatile and the best.
Sorin with Gisela & Give no Ground or Brisela is crazy good, and his access to life gain in both cards and creatures plays well into his third ability. I’d say his only downside is all his abilities require you to have creatures on the board to use, so he can be hard to pull himself back if your board state gets wiped. His +4 in black and white is great, and his access to removal from both colors is always useful.
All in all, though, I like that he’s just really hardy due to his ability to gain life. He’s a planeswalker I feel safest taking into new content while learning.
I will refrain from voting. Last time they asked me my favorite planeswalker, I told them that it was Saheeli Rai. And they butchered her…
I’m still voting saheeli because she’s a blue walker with insane mana generation.
Even though I like Ajani better, I think Kiora is probably the best overall. Blue/Green is a great color combo, and her abilities are great in almost any deck.
Kiora, because she consolidates more power cards and ramp ability than any of the others.
After that, all have varying pros and cons that really suits an individual’s cards more than anything else.
The mana gains of Ajani and Sarkhan, which once were consistent and smooth, are starting to fall behind the curve, though.
Best is 100% subjective and dependent entirely upon your card collection.
Card inventory notwithstanding, Kiora probably takes the cake here. Her 3/3/0/0/0 works fine due to green ramp and she’s able to access all of blue’s oppressive control. See also: killwind.
For me personally, I find that my nodes often contain Nahiri, Sorin, Arlinn, and Sarkhan. My blue collection is not great and definitely holding back my Kiora, Saheeli, and Dovin.
A lot of people give Arlinn grief. I don’t personally understand it - she’s my second most consistent planeswalker, with Nahiri on top. Maybe it’s a card inventory thing?
She’s decent, but if you don’t have good wolves to play, all but one of her 6 abilities are locked out. Id be curious to see what’s in your arlinn deck. I was so happy to see a red and green combo pw before she came out, but since then, I’ve been slightly underwhelmed with her performance in practice.
This is what I use for my non-WW decks:
Fertile Thicket
Nissa's Pilgrimage
Inner Struggle
Demolish
Animist's Awakening
Devil's Playground
Season's Past
Zendikar Resurgent
Harness the Storm
Olivia, Mobilized for War
Devils/Olivia/Resurgent are best buddies, and the SP helps me cycle back the supports I inevitably destroy with all my gem conversion.
For events that require werewolves I do end up playing Ulrich & GRB, but I’ve been lucky with my access to those.
I might be an oddity - I play my PWs for the color combos they offer me rather than their abilities. Sarkhan is a lot of fun with HtS & black’s cheap removal. Dragons? What are those?
screw all of you with Olivia 
I have all of those cards except zendikar resurgent but maybe brain in a jar is a decent sub
But I don’t even have dragons to play with sarkhan yet he is one of my most consistent pws.
I voted for Nahiri. Her 3rd is the one skill that you can use to win immediately even when all looks hopeless.
Nahiri by a short step before Kiora - and that short step is because Nahiri plays better without top mythics, while Kiora needs a really solid cardbase to do her wonders…
I wanted to vote Saheeli, because of her amazing mana gains and her access to blue and red. However, her abilities are just sub par unfortunately. I voted for Kiora even though she’s not my favourite, mostly because of her amazing versatility with abilities.
“Best” for me is pretty subjective. I feel Kiora’s the best overall, but…
So I guess Kiora is a jack of all trades, master of none.
Sure, color combinations are the primary reason to get excited about planeswalkers, but having useful abilities is certainly better than having useless abilities. Plus, Sarkhan doesn’t need dragons. He can MAKE dragons from any creature. He can kill his own Devils to kill your creature and give him a 6/6, he can pop his own Despoiler for a free dragon, he can kill an Amalgam and bring it back the next turn.
Arlinn, by comparison, is useless. Her abilities just sit there.
Red/green’s biggest problem is that it’s a one-dimensional pairing that Arlinn exacerbates.
your experience and mine differ and that’s okay.
My Arlinn is pretty killer…
But I got lucky with pulling Ulrich, Geier Reach Bandit, and Descimator of the Provinces for her. She’s one of my strongest decks, but largely because of cards, not so much because of her.
Wouldn’t Nahiri do just as well as Arlinn with those cards, if not better?
Maybe? Though it’s also planeswalker level. I just got Nahiri the last time she was in the store, so she’s still pretty weak, whereas I got Arlinn a while ago and have her at 60. Plus Arlinn can tutor them up whereas Nahiri can’t, and Arlinn get benefits from green mana ramping like Nissa’s Pilgrimage or Fertile Thicket. So there are different strengths to each.