The performance is amazing. It runs incredibly smoothly on my computer despite being 3D, while League in an isometric view lags on occasion and averages 30-45ish fps.
The gameplay is pretty alright. It takes getting used to, including item building, just like League was when we were newbies. I suggest changing your keybindings, which is pretty easy (I use Q2ER for spells, 1 and 3 for items, and F and V for actives).
Flexibility is amazing. It's not like League where you always run flash and then a meta summoner, you can actually purchase two actives (no item actives, which means less button pressing when you already have ASDW controls). Most actives from what I seen are viable, and the "cleanse" active is pretty damn useful in this game. You can even upgrade your actives in an upgrade tree (using gold) and even change it.
There's multiple game modes, and everyone one of them has their own first win of the day bonus. All of them individually. You can get like 500 extra in-game currency, where several of the gods cost 5500 (you heard that, bby. League, eat your heart out). It's not like League, where everyone plays SR and occasionally ARAM and nobody knows how the hell Dominion works anymore. All of these game modes exist, and all of them are played, and they are all fun.
Wards are insanely cheap compared to your gold gain. And they take up a consumption slot rather than an item slot (and there's a mana/health potion hybrid for the same price as other potions if you're concerned about that).
Every single god is broken in their own way, and there's counterplay to everything. Several gods can be played in several ways, depending on how you combo their abilities.
Jiggle physics, if you're into that kind of thing.
You get your ultimate at level 5. Level cap is 20.
If you're a fan of Greek mythology, you can play as Aphrodite, Athena, and Artemis. Nothing beats kicking ass in high heels (I'm not shitting you, Athena is badass like that).
You have to aim your "autoattacks." That means you can dodge them too! D: It adds a level of difficulty and counterplay to the game, and yet I somehow find it a lot more fun. It's like comparing TERA to WoW, and I would always choose TERA. And you can block attacks that would kill your allies. Tanks are so much more useful in this game!
I believe you can buy skins with in-game currency (hella expensive, but that's fair imo), and you can even get gems (basically RP) just by logging in six-seven days in a row (totally worth it). Every god is priced at 200 gems without exception, making it look less pricey and cash-grabby.