I've used Falken 451's and Hankook RS2's on my IMpreza. The 452's are the same rubber as the 451's, with a better, quieter pattern.
451 - take around 1000+ miles to break in. Dry grip is excellent. Wet grip is outstanding, world class, as good as it gets. Sidewalls are stiff, so turn-in is sharp. Breakaway is outstanding, very progressive. No tramlining. Loud-ish, but not bad. They run wide. I drove 16miles of canyon every day, VERY spirited, and got ~25-30K. Cheap overall, a downright steal when you consider they can go up against, or beat, tires costing twice as much. I don't know what magic material they use for these: wet grip, dry grip, awesome heroic breakaway, and wear like iron. For cheap. Yeah.
RS2 -Dry grip excellent > outstanding. I'd say maybe 10-20% more than the 451's. Wet grip only good, which is to say as good as all seasons I've tried, and not at all a problem; you just can't get silly like you can with the 451's. Sidewalls are soft-ish, so turn in is more vague, and you can feel flex in them. Breakaway is less progressive than the 451, but still very good. Very minor tramlining. Hmm, can't remember noise on these. Narrower than 451's. A bit more expensive than 451's. Wear like ASS. 15k is good.
I had 451's, tried RS2's, and went happily back to 451's. The RS2's are only better if you need ultimate grip. THey do grip more, but don't feel good doing it, they're soft and dull feeling. Despite the extra grip, something interesting happened: I discovered I prefer a bit less grip. My Impreza was very well set up, supension wise, and I had WAYYY more fun utilizing the sharp turn in and awesome breakaway to slide sideways onto freeway onramps, rotate the rear end through the canyons with wheel input, and so on. The limit in the dry was enough higher with the RS2 that I was not comfortable 'having fun', as the speed needed was so high, and inputs needed were so aggressive, that it became, um, unfun, ie stupid and dangerous.
That's my story and I'm sticking to it. Hope it's useful!
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