As far as I know, the plugin Avira Browser Safety (ABS) will use cloud lookup to check the url, while the Web Protection module (WP) will scan the network traffic with the webcat libraries stored in the local.
1. The database of url is updated more frequently in the cloud than the local. So there may exist some malicious URL that can be blocked by ABS, but cannot be blocked by WP, before the webcat libraries are updated.
2. The scan and analysis of WP is performed in the local, so it would be heavier than ABS, which only lookup the results stored in the cloud.
3. ABS has some other features that WP does not have, such as traffic light (showing different icons for different results in the search list) and tracking protection.
4. ABS can only analysis URL. By contrast, WP will scan both URL and the traffic payload. Consider a webpage which contains malicious payload such as Trojans. If its URL is not blacklisted in the cloud, ABS cannot block it, while WP is possible to block it.
5. The traffic scan of WP does not depend on the browser, while ABS can only be used in Chrome, Firefox, Opera, and IE 11 on Win 7.
Avira Browser Safety is not that good, it blocks too many stuff like some pictures or some video content on website's
There are similar alternatives for ABS
Edit: ABS is much better now with all the bugs out.