Well, if you are interested being as anonymous as possible, Tor is far more interesting. The VPN provider may not know who you are but it does know your IP address and the website you are visiting, which is almost the same if it comes in the hands of those you probably want to avoid knowing it.
With Tor on the other hand, node know each other's IP address. As you make a network request with Tor, it will pass through a number of nodes, usually 5 I thought. Of these 5 nodes, only the first one knows your IP address and only the last one can see the request you send. Supposing you use SSL as much as possible, the last node only knows the IP address your request is send to.
All intermediate nodes know nothing about you. So you are in fact the most vulnerable for the first node, because he knows your IP address. But he has no clue what website you are visiting, so no single computer in the Tor network will be able to see what you are doing.
Besides, sending a transaction with Tor does not have to be slow. That's just a small packet. You probably mean that syncing with the network and downloading all blocks is slow. Well, there is not much of a point for doing that via Tor. None of your addresses are sent along with block requests, so you can safely sync blocks over VPN or regular internet. The most information the outside world will get to know is that you are downloading Bitcoin data. But using a VPN that accepts Bitcoin, I doubt if they would be eager to share that information with others.