Managing assetbundles (caching vs non-caching)

We're working on implementing a system where the user can cherry pick several different packs (with audio and image assets) to download and we figured assetbundles would be the best approach for this.

We have an .xml that lists all the assetbundles and their version (for updates).. and via www.LoadFromCacheOrDownload() we are able to download each of them perfectly to the cache if the versionnumber is higher than whats previously there.

However, we also want to offer the user to delete packs by choice.. apparently there is no real support for this except Caching.CleanCache(), which removes all of it, or some work around with setting Caching.expirationDelay to a low value. But coming across the limit of 150 days this makes me wonder if we should use caching at all.

Basically my question is; Would it be a better approach to not use the caching system and use a regular www download to the persistentdatapath instead? (with our own system to remove/update the assetbundles)

The docs recommending WWW.LoadFromCacheOrDownload() is also why I'm a little worried as they don't really give a reason as to why. Does anyone know?