Some tech trees offer 'upgrades' that serve the same function and are an improvement in every way to their predecessor -- a strictly dominant strategy, and therefore it's not a choice, it's a no-brainer.
In some games (Endless Space:Disharmony, for example) new technology is hard-coded to imitate such a forced decision, even though the tech is only a weakly dominant technology. There are times when a price, time or space advantage could have been better, but the interface is designed to prevent such considerations.
If we consider the environment, (such as Galactic Civilization 2's rock/paper/scissors weapon & defense systems) then it can become an interesting interplay. Guns aren't automatically inferior to Lasers, it's a matter of what the other player is doing.
There's also a mentally compartmentallised problem with price. 'Upgrade' techs almost always have a higher resource cost, be it materials, time, space, research points, whatever. But it's not a tradeoff, because that implies a set of valid choices, which is not the case when there's a strictly dominant strategy. So the game ends up senselessly inflating the price of stuff.
Edited by AngleWyrm, 24 October 2013 - 04:24 PM.