Syndra vs orianna vs lissandra

It really depends on what you want out of your mage... Syndra is the most difficult to use/master of the 3 (altho none are particularly easy) but her benefits are high AOE damage and mobile casting. Orianna is the most well rounded of the 3 with attack/defense/utility in equal parts, as well as probably the best consistent harassment of the 3. Lissandra is definitely the best for CC (if not the best in the game...) and can sacrifice her attack power for defense. I like all of them honestly...but of the 3 i use Lissandra most currently. I used to use Syndra as my secondary but i just haven't lately. I got lots of quadrakills with her back in season 3..

Syndra is an extremely solid burst mage with strong laning and self peel while having a lot of combos. Orianna is a solid laning phase utility champ that has extremely strong team fighting. Lissandra has mediocre laning and decent teamfighting while also having very strong roaming potential.

Personally I think Syndra is probably the best of the three but they fill different roles. Syndra for stomping and carry deleting, Ori for wombo and teamfight orientated comps, and Lissandra for teams lacking CC. I love all three, and despite saying Syndra is probably the best of the three I enjoy Liss the most. Her unique ganking paths leave her very entertaining to play.