Uncapped is great for not having to worry about how much you are spending. You are however, spending a bit more than you need to ... most months.
For home use, generally you will pay less and get better service on a capped account, but you do have the hassle of having to set the amount of data beforehand, or pay extra some months for auto-topup. If you don't know what your usage is like, sign up for uncapped for a few months, and convert to capped if you still care about saving money or getting more bang for your buck after some time has passed.
If you go for capped, you need to guesstimate how much bandwidth you are going to use. Before you actually start to use the internet for something interesting, your smart phones and computers are going to use up a good chunk of data just to stay warmed up and up to date. These statistics only vaguely correspond to reality:
iPhone - 250MB per month
Android - 150MB per month
Other feature phones - 10 to 100MB per month
Windows updates - 500 Mb per month
If you don't like maths and estimating, do it the easy way.