Which of these two champs should I go for between 
and 
? Who moves better, hits harder, sustains more, has better CC, and can play more roles. I would also like the cons and pros too along with reasons why OR even why not if you don't mind. Please feel free to post your personal insights and feelings too. Thank you.
MrPerson102 votesMost of these questions are pretty straight-forward Both fit into two roles well. Irelia top/jg Diana mid/jg - diana JG has become much harder to use effectively though with the new jungle hitting as hard as it does. (edit, I suppose Irelia could fit a support role as well in low elo, however definitely wouldn't recommend it)
Both have a dash, Diana's Q/R gives her a free dash from R to a moonlighted target, Irelia's Q gives her a resetting dash if it kills her target.
Irelia has true sustain along with true damage on her W. Diana's W gives her a shield with damage but no true sustain
Both have a form of CC - diana's E is an AoE pull coupled with a slow, Irelia's is a slow or stun based on comparative % health. (ex, Irelia at 50% health, enemy at 52%, she stuns. Reverse %s and she slows - this essentially ensures she doesn't have a stunlock when also winning trades)
You have to bear in mind they hold very different roles.
Diana serves as an assassin who's able to stick to her targets particularly when caught out, a great pick into 
for example.
Irelia serves best as a bruiser with her 
core, can dish out quite a lot of burst damage with just that as well as being able to take a fair amount of damage.
For me, I like Diana. She's just funner to use and isn't nearly as unforgiving as Irelia.
QuantumLight2 votesdiana jg has 2 issues - blue buff is practically required, and her ganks pre-6 suck. besides that shes awsome. clear time is stupid high, and post-6 ganks are slightly above average. the new jg doesnt really hurt her as much, provided you can spam skills till mid/late game, which is why u need blue.
MrPerson101 votesPrecisely, only issue with that is blue doesn't last nearly as long as you need it to even with your utility mastery for extra time (I can't remember the name of it for the life of me)
QuantumLight1 votesidk im usually fine. just take it, farm jg untill its gone, take 2-3 more camps, b, take 1-2 camps its up again.
its called runic affinity. :)
and i dont use it... i go 21-9-0 masteries.
MrPerson101 votesI assume you also run some fair CDR in masteries?
Idk, I guess I'm more partial to junglers with the strong early game pressure 
(even though I'm a terrible Lee) as opposed to those waiting until later to have effective ganking potential
QuantumLight1 votescdr at 1: 5%
early pressure is not diana's forte... i can totally see why u dont use her as much :P
Scrambled Anivia1 votesirelia is a safe monster in the top lane. 2 item domination. diana is more fun to play. and can play mid, jungle and maybe top.
MrPerson101 votesI wouldn't call her particularly safe, as if you get behind she's really hard to catch up with.
Though she is certainly a monster in top
DreadnaughtLoL1 votesThanks for the imput guys I appreciate, it. To be really honest I play top more than 80% of the time, but there's always that moment where I may have to go to a different role/meta. Seems like is the best choice for me.
Buff Nutskin1 votesIrelia can trade with almost any top laner early game. Level 6 she becomes stronger than everybody except for maybe Riven and Darius. Diana often has to use her shield and Q just to get farm early game, but at level 6 she becomes a major threat if you aren't too behind. Obviously, Irelia has better CC and Sustain than Diana, although Diana has more burst. Depending on the team you're with and against will depend on which is more useful.
Oddysseas1 votesIrelia is top lane beast, diana gets countered hard in mid lane till she hit lvl 6.
If you like top lane go for irrelia, if you like mid go for irelia lol.
Irelia ftw
MrPerson101 votesIrelia mid's trash, I've tried it as a troll pick
I know it was more a joke than anything, but some people will take it seriously
Hard4Hamsters1 votesThey are similar play styles, but Irelia will generally be the better "all-around" choice. Diana has much more burst, but Irelia is more reliable and has more sustain. Diana can be played mid, jungle, or top. Irelia will generally avoid going mid but she potentially could. Typically though she stays top as she is one of the strongest top laners in the meta right now. Irelia brings the possibility of harder CC and has 3 damage types so she is hard to counter defensively. Diana does mostly magic damage. Also Diana should not be initiating many fights if you build her as an assassin/mage. Irelia has the option to initiate a fight by jumping on a squishy target, and can possibly get out alive even if she is targeted as she has the built in tenacity of her passive. Irelia's ult isn't really a power spike and it's really one of her only weak points. She is strongest in the mid-game after she builds her Triforce but is relevant in the late game due to her sticking power and decent damage output even when building tanky.
Diana is a great assassin right now and her damage is scary. Her level 6 is a huge power spike and can mean an easy kill against your lane opponent in the early game. Her roaming and snowball potential are high and she doesn't really have mana problems if you start double dorans ring or take a flask. She again falls off later in the game, but her passive procs on towers and inhibitors so she can take them quicker than most AP building champions. The problem with Diana is that she is very dependent on hitting her Q and it is a strange and difficult skillshot to hit, but if you can, her damage output is comparable to Akali with a Q, W, R, Lichbane/Passive proc/(Nashor's if you build it); if they're not dead yet or if they flashed away R again E AAs and Lichbane will take care of any squishy/semisquishy target.
As an aside, I will sometimes build Diana as a tanky initiator with a build that you would typically see on Irelia 
. The AOE slow and constant shields you have as well as having a lot of stickiness makes you a great initiator if you get someone out of position. You probably won't do as much damage as an Irelia but with the right team comp (think 
). You can wreak havoc on the enemy team.