With Redstone you can create wiring and circuitry. Using this, it is possible to create complex devices and even "programs". Unfortunately, the size of such projects usually tends to be massive in the in-game world and difficult to navigate. In order to reduce the size of the project, does anyone know the most space-efficient construction of the AND and OR logic gates?
There are several ways of constructing the gates you are interested in. I would trust what's already well documented on the Minecraft Wiki:
From the wiki page there are several considerations you have to keep in mind in making the decision of which design you go with.
Barring changes to Minecraft I'm not sure you have many other alternatives (though I'm sure there's a mod out there with more compact gate support.)