What is better option, electrum or blockchain.info when using Tor, regarding anonymity? I read here: http://www.coindesk.com/bitcoin-tor-anonymity-can-busted-2500-month/ that it's possible to deanonymize Tor user who uses bitcoin protocol. But, they didn't explained how. They only explained that you can use DOS prevention in bitcoin protocol to block all Tor exit nodes from bitcoin network for 24 hours, and than add your own Tor exit nodes, and force all bitcoin traffic trough it. But that still isn't enough to deanonymize Tor user, you still need to control Tor entry node for particular user. On the other hand, if this article is right, it is better to use blockchain.info for anonymity, since it doesn't use bitcoin protocol directly.
You're most likely fine with electrum.
Since the threat described in the paper only applies to full nodes you should be fine when using electron over Tor, since the electron collects to specified (and somewhat trusted) electron servers and not to p2p nodes. Electron also uses it's own protocol.
For more anonymity you might want to connect to a electron node through a hidden service.
As far as I understood the paper your real IP could be revealed through a cookie (in the bitcoin client) which is set by attacker and can be read through the Tor IP and your real IP.
Personally I wouldn't use the blockchain.info wallet since it only connects to blockchain.info servers and therefore isn't decentralized at all.