I have used both the OEM and a CoverCraft Evolution.
The custom fit CoverCraft fits very well. Better than the OEM.
I have one for the S2000 and NSX. again the fit is outstanding.
The OEM shrinks over time with washings.
The Evolution provides some physical protection as it is a 4 layer cover. 4 year warranty.
Both these covers are used indoors only, but the CoverCraft Evolution is an outdoor cover.
One word of advice. In a parkade, over long periods of time. (winter) The dust from the concrete can take its toll on any cover. I suggest a cover for the cover. That dust needs to be removed from the cover before putting back on the car. With out attention, a cover can do more harm than good. Use a cheap semi-fitted plastic cover over the fitted cover for this application.