You'll probably use more because you won't be going to the mobile version of each site, you'll be going to the full site. Even so it depends on your data limit. If you have a high one then you will be OK, just don't be on it too long. That's another thing to look out for.
If you plan on using it all day then test it first using an app like 3G watchdog. Connect for an hour or so, disconnect and 3G watchdog will add on how much you used to your current limit. It doesn't update in real time though hence the connect/disconnect.