I have mostly played Terrans. They are not in anyway underpowered. For a start, you can customise all abilities yourself so you can make them what you want them to be. On colonisation, it is far more the players skill than the racial abilities (although these do help) - on larger maps I always start by research down the engine route and have an upgrade Coloniser for each step. I always massively outcolonise the other AI by at least double playing on Tough.
Just make sure you buy a lot of stuff. You can either focus on buying factories etc and specialise Earth towards Military production to crank out colony ships. Once you grab a planet with a decent PQ, buy a factory or 2 and build a starport so that you have doubled your speed at colonising. Alternatively, dont build up your military capacity - drop the slider to 0% at the start and build infrastructure instead then just rushbuy all your colony ships. Or use a combination of the above. I tend to start with the latter by rushbuying a load of ships by which time my infrastructure is good enough to push fast colony ships out every couple of turns.
Make sure that you redesign the starting colony ship and have 1 for each level of engine, then you dont need to mess around every time you research a new tech.
