As far as overclocking, you could overclock both. However, overclocking is not "covered" under warranty, so if it is damaged from say too much voltage, you are screwed. That, and given I would not recommend it to someone unless they have some tech savvy. However, both cards are likely to overclock some, but the 460 I linked to is overclocked so much over a standard 460, you probably do not need to overclock it. Especially compared to the performance you would get from the 550 Ti.
But get what you want, it is your money.
Actually overclocking is covered by warranty, even if you do burn it out, EVGA will still replace it and overclocking the 550 TI will be better, not to mention that either card will work fine for pretty much anything he wants to do.
http://www.evga.com/forums/tm.aspx?m=307323&mpage=1
















