I have 205/55's on my car and they feel a hell of a lot better than the stock 205/60's... The ride is alittle more harsh, but it does handle better and gets better traction with the wider tire...
But for a reccomendation I would go with the 225/50's, wider is better for traction and handling, plus I think the wider tire would look great...
But either would be good... the 215/55 would be taller and throw off your speedo by about 2.5%, but one + is it would ride smoother, the - is it would effect your steering responce and overall handling...
Just my thoughts