Essentially, Netrunner and Star Wars have two pools apiece. New Runner cards don't directly impact the Corp pool and vice versa. So, each of these pools grows at half the rate of the game as a whole.
Combinatorics come into play measuring how many new deck combinations there are depending on the size of the pool. Most games adjust by individual cards. Star Wars has vastly fewer deck combinations due to a deck only being 10 "things" in size. Fans of the game may claim that more combinations are viable compared to single-card-adjustable games, I'm not getting into that. What each game allows you to do with cards also makes a difference but is hard to measure so I'm not getting into that right now either. But mathematically two half-pools do have fewer combinations than a single pool of equal size.
Effectively, I think that Arkham Horror will feel like your options expand faster than LotR at a similar expansion age. However, as with any new LCG it takes time for the pool to grow and get a good feel for how the game is going. Let's meet back after the first expansion campaign is done and the boxed intro to the next one is out with another set of new characters. That'd be about a year from now I think and probably an excellent point to evaluate from.