I always thought that the Ghost Summoner Spell was essentially the more "noob" version of Flash. Recently, however, I have seen several pro-level games (MLG, PAX, etc.) where the pros do indeed get Ghost instead of Flash. I don't understand the logic behind this and was hoping someone could enlighten me. I've seen it a couple times, but the champion I specifically remember it on was a Shen.
The only thing I could think of was that Shen can already use Taunt to get over walls and obstacles, so perhaps Ghost would generate more distance in the long run… But even this seems like a stretch.
Thus the question: When and why is it more beneficial to get Ghost over Flash?
Best Answer
The way I think about it is like this:
if your champion has a snare/root/disable/whatever, then Flashing in range and using it (pretty much) guarantees you can keep hitting them for a good while at least. Think Darius and his W-E combo, you can Flash in range of a champion, pull him to you and snare, then just keep hitting him.
if however your champion has no such disable, Flashing alone will get you one hit, maybe an autoattack too, then they run away. Here Ghost is more beneficial because you can keep chasing them. Shyvana is a very good example of this, although I like Ghost on Fiora also because her sprint ability is kind of short duration compared to the CD and she has nothing else.
You should however consider that Exhaust might be a better choice over Ghost for chasing/ganking purposes where Flash isn't "the right choice", because in addition to the snare, it also nerfs their damage output, so you can use it as a peel for your carries (or just straight dueling). I use Exhaust on both Nocturne and Shyvana for this purpose.
The argument above that Ghost is good at escaping... I don't know about that. You never really leave melee range if they snare you during it, whereas Flash opens a gap for you to let your snares run out and stops damage income cold. Ghost is also a one trick pony, whereas Flash can net you a huge tactical advantage by Flashing over walls that champions without Flash would have to otherwise slowly run around, or lets you escape turret damage instantly etc etc.
Try them all in my opinion, you'll get the hang of their strengths and weaknesses after some amount of games. I'll tell you that I miss Flash the most when I run Ghost or (more often) Exhaust, but I'd still never run a Flash Shyvana.