You really shouldn't shop for your parts based on what the warranty is. Buy the quality of the part, not the warranty. That is one of the biggest mistakes most auto parts customers make. Autozone offers a lifetime warranty on their brake pads, which are complete trash. They offer a 1 year on their Raybestos brake pads, which are far superior in quality and actually, some grades have a lifetime warranty from the manufacturer (Autozone just won't honor it).
OE parts are often times cheaper than aftermarket when you have a dealer account. Gaskets are a prime example... . much cheaper at the dealer. Chassis, I'd say could go either way. Your average joe is going to pay out the *** at the dealer, though, and such is the business. I don't agree with it, but that's the way it is.
I would say that an aftermarket part that doesn't have a grease zerk is definitely no better than OE, and could very well be lower in quality. I have never sold chassis without grease fittings. That's almost unheard of in the automotive aftermarket, unless it's impossible to install one.
Any chassis component that cannot be greased, and further, purged of old grease, dirt, and metal filings will wear prematurely. I'd go with whichever is cheaper unless the aftermarket part was of questionable quality, and go with the best you can get next time (and keep it greased!).