If I want to make my Windows more secure, should I use a standard account or UAC will suffice? With UAC I don't need to type passwords to perform admin tasks.
A standard user is a little more secure because they can't perform administrative tasks at all. With UAC, you run very close to that same mode, but it is more convenient to run those administrative tasks as necessary. There may also be things, like modifying some Windows settings, that are not convered by UAC unless you increase it to the maximum level.
You are probably well off with UAC and the default setting, imo.
On Microsoft Technet it says that you should never disable UAC and users should run as standard users...
Here is a nice post on Why you should never disable UAC
Bottom line is, if you want to make your Windows more secure leave the UAC enabled and run as a standard user.