I'm deciding between buying a Canon 50mm 1.4 or 1.2. Is the extra price for the 1.2 worth it, because of the better build? I've read reviews that both the 1.2 and the 1.4 have focus issues. Is it worth it to get either? And finally, will there be an update to the 1.4 or 1.2 anytime soon? Thanks.