There is a substantial difference between the way Usenet and BitTorrent works. Usenet has the major advantage in that the content is located on dedicated servers, which means that as long as your provider has content you are interested in getting, it will generally download as quick as your ISP connection can handle. Unless you manually upload something to a Usenet server, you are not sharing anything out when downloading from Usenet.
BitTorrent (including Vuse) on the other hand is decentralised and is totally depedent on sharing to work, which means that each download requires one or more other peers to upload to you. As you download a Torrent (file or set of files), your BitTorrent client automatically shares what parts of the Torrent you've already received to other peers also downloading this Torrent.
There are a few other differences. Usenet providers only keep binary content (e.g. music) for a limited amount of time, e.g. 240 days for Giganews. With BitTorrent, a Torrent can be fully downloaded as long as there is at least one seeder of this Torrent online for the duration of the download.
I currently have Giganews and so far have been happy with them over the past two years. They have a 240 day binary retention (i.e. they keep files for 240 days after the date they've been posted on Usenet) and charge $12.99 for 35GB / month (nearest match to what you're using), but they don't rollover unused quota.