Aftermarket Vs. OEM

So... again I'll preface by saying I am very knowledgeable on which is better when it comes to my Hondas, and I can say without a shred of doubt that OEM Honda parts are the only way to go for reliability.

Now that the little 330ci is eating my wallet these days, and there are quite a few parts that are known to fail, my big question is:

Are the aftermarket replacement parts more reliable and better to use? I am finding very little with respect to this other than the metal impeller water pump debate. I'd rather purchase a higher quality part if it's made by someone else that will outlast the OEM item, but since I am new to the 3-series game, I need a little help. I know which sites to browse thanks to this forum, but would love to hear about the quality.

Thanks!