18s definitely look better than 17s. But 18s make the stock brakes look absolutely puny, cost more, weigh more, give a harsher ride, and don't provide that much of a difference in handling. In fact, alot of autocrossers are using the stock 16s or lighter 16s with upgraded tires. That tells me that the quality of the tire and weight of the wheel has more to do with performance than the height of the sidewall. I'm happy with every aspect of my 17s and would probably never consider 18s. It's a matter of personal preference.

 

I went with 18's jus for the look...if I was going to practicallity I probably would have went with 17's..they are the better choice...and yea 18's make the stock brakes look small

 

The difference between 16s, 17s, and 18s and their relative smoothness depends greatly, greatly on tire choice. I put 18s on my wagon with 225/40s and honestly, it was nearly as smooth as with the 16s. The key was the tire - I used the Sumitomo HTR ZII - a tire noted for it's smoothness.

For comparison's sake, the 225/45-17 in the same tire would theoretically be a bit smoother, especially on a bumpy highway with many expansion joints.

I have 17s on the wagon now (because of weight and cosmetics, not smoothness) and that's what I would recommend. The moral of the story: you can get an acceptable ride with 18s on the WRX, it just depends on which tire you choose.

 

Good info dexter, thanks

 

If you can find the Rota Slipstreams, then you've got your wheel. Really light and 16x7. I almost got them, and then got go fast stuff instead. I know suby_dude used to carry them. Try asking him where to get them.
-Etch