Hi I'm Primowang, I main support on the NA server. My favorite champs to play tend to be the AP supports, but I also enjoy trying out some slightly off-meta builds. I originally tried out Orianna as a poke support such as Karma or Lulu, but quickly learned that her mana costs were definitely way too high early game to play effectively bot lane as an aggressive support. I then discovered that Orianna can actually excel really well as a defensive support champion similar to how Janna is typically played. Orianna has arguably the strongest shield that can be cast on allies in the game due to its passive adding a whopping 30 armor AND 30 magic resist to its target when fully maxed.

While Orianna is considered by many to be one of the most difficult champions to play well, she is definitely one of the most fun and entertaining to play as well. Pulling off a play with Orianna feels extremely rewarding because learning to use her effectively can sometimes be a challenge because the mechanics involving her ball are unlike any other champion. When it comes to her play style bot lane as a support, she is most similar to Lulu or Janna. Like Janna her shield is her biggest asset in letting her ADC win trades in lane, but like Lulu using her effectively involves the placement of a pet (Pix in Lulu's case and the ball in Ori's). What she brings to bot lane that is different from these two is that her shield applies a passive buff to its target's resistances, even when not active, meaning that even when the shield is down, your ADC will still be taking less damage in comparison to a Lulu, Karma, or Janna shield. She also has the utility to speed allies and slow enemies that each of these supports have. But while Lulu and Janna's ult abilities are more often used as disengage or counter-engage, Orianna's ult possesses the potential to be a powerful engage that can be cast upon an entire team. So in summary she has a much more defensive shield compared to other supports, but a much more offensive ultimate that can still be used as a strong disengage as well.

Pros:

Strong shield that gives constant bonus armor and magic resist. Its mana cost does not increase per rank. Cast range on shield is 300 units longer than Janna's and 450 units longer than Lulu's.

Excellent auto attack harass due to passive, similar to Lulu.

Good utility with up to 40% speed boost and slow. Ori's ball can safely check bushes or fog of war. Has a very safe play style, similar to Janna.

Very powerful engage and disengage with ult. You can quickly and easily peel off assassins from a great distance by simply leaving your ball on your ADC and ulting.

Very strong pick against poke compositions.

Very uncommon pick, enemies will most likely not know what to expect from you.

Cons:

High mana costs makes it inefficient to use abilities aggressively. Any form of harass should mostly be dealt through auto attacks.

Very complex play style making it easy to miss abilities entirely. Losing track of your ball's location can cause you to waste an ult.

Will not output considerable damage without building full AP.

Shield is not instant cast unless Ori's ball is already on its target.

Weak against targeted hard CC such as Annie's or Taric's stuns.

Winning lane relies heavily on the ADC's ability to kite and dodge while utilizing your shield and speed boost.

Very uncommon pick, teammates will most likely not know what to expect from you.

In summary, in comparison to supports that perform similar roles, what Orianna makes up for from having poor mana sustain early on, low damage output, and difficult mechanics is the ability to buff and peel for her allies from a very safe and far distance (1100 units), a tankier shield giving constant armor and MR, and a strong engage ult that can be used aggressively.