I think if you're going for a Rimowa, go with the aluminum because that's what they're known for.

I had been wanting to buy a Rimowa trunk for a long time (checked bag), but finally decided against it. It seems the new generation ones (made after the company was bought by LV) has had mixed reviews (but still good). But my main deciding factor was that service centers are few and far between - and there's actually none where I'm at right now. I eventually went for a Tumi 19 degree aluminum (half the price on sale compared to a Rimowa).