For a short time the USA credit card companies were automatically sending NFC-based cards. Everyone I know that received one watched as I used an Arduino and cloned it. Then they sent the card back requesting the safer cards without the silicon-based security hole (called NFC).
SIMs have been more secure than NFC for quite some time. So, I assert that the the need for improved security should be to bar the ability for attack by a script-kiddie with $30 worth of equipment (or an Android phone now - see Electronic Pickpocket app at Play store - Free).
While many might like the speed and convenience of ticketless payments, lots of people are worried about the security aspects. Witness, for example, all the adverts for wallets and passport covers that act as NFC shields. The idea of having a payment card that broadcasts my account details makes me very concerned!
The idea of a single card (or device) that authenticates my payments is all very good, provided that it cannot be cloned, it stops working if it is lost or stolen (and I can get a replacement very quickly, even if abroad), and it does not reveal information about me beyond that which is necessary for the transaction. A tall order!
There is also the issue of how the information about payments is stored and used. If I contact my mobile phone operator, my identity is validated by easily-discoverable information... and a PIN which can be discovered by many employees. I do not call this secure, so entrusting more information to them does not seem wise. basically, all 'security' and 'trust' seems to run one way, so it seems sensible to limit ones vulnerability until systems offering mutual trust are put in place.
@ip2design, I agree with you. There is no reason for SIM based security to be slower. But the security layers implemented by the service providers --and mostly by the SIM system integrators-- have serious implications on speed.
Looks like TfL and other transit authorities have been working closer with cell companies and system integrators and the issue is being resolved.
We all know that NFC-SIMs and embedded Secure Elements are fast enough to perform access control the right way at the right speed. Most of the ICs are now based on 32-bit core running at 30MHz with hardware crypto and secure OS.So, there may be some tricks to optimize the solution.