french press vs. chemex - oil absorbed by chemex filters?
The Chemex process does absorb oils, and also reduces the total time the coffee grounds stay in direct contact with hot water. But the issue is less about better-vs-worse, and more about your preferences wrt the characteristics of how you like to drink your coffee.

French Press yields, assuming all else is the same, an earthier, more viscous brew with more pronounced bitter notes that many people prefer. This is related to the presence of oils and suspended microparticles, much of which the Chemex filter removes. 

Assuming the same grounds-to-water ratio and the same bean, a Chemex process will yield a coffee infusion with relatively sharper high notes, enhanced acidity and lowered bitterness. For coffee varietals and roasts that have more delicate, perfumey elements, Chemex can be a preferred method. Many coffeeshops prize these more floral, wine-like elements in their coffees and want their customers to experience them. 

Besides choosing to showcase the more delicate elements of the coffee beans, many high-end coffee houses also have logistical concerns facing them as they work to assure the same coffee experience cup after cup. Assuming the patron receives a ready-to-drink (or ready-to-lighten/sweeten) cup of coffee, Chemex offers a process that is easier to measure, time, brew and dispose/clean up than French Press when presented with a stream of customers. While, French Press is easier than Chemex if you give the press to the customer to press and pour when they wish, that means the coffeeshop cannot control the final brew quality, which is often what they prize. Assuming the French Press is poured into a carafe, this problem can be ameliorated, but dumping, rinsing the pot, then unscrewing, rinsing and rescrewing the press is more challenging under time pressure than simply lifting out the Chemex filter and discarding.

Personally, I prefer French Press. I like the heavier, more viscous brew that the process yields, and I lean towards Half-City or medium roasts, which are lower in bitterness in the first place. 

Here's a good example of a method very similar to what I do:
http://stumptowncoffee.com/brew-guides/press-pot/