A vote for civ5 here. I remember being very disappointed with Civ4 for not having hexes. Dont really want to go back to squares. I did like the whole culture and religion aspects. The religion was very good imho. And culture was fun too. Civ5 misses the religion almost as if they are keeping something on hold for the expansion. However I'm enjoying 5 as it is. I like how they balanced city vs expansion. I like how the hexes make it so you dont have to plan city positions to the exact mm. I like that a lot. I like the balance on the different civ traits. Dont remember 4's being as good.
But if it crashes for you and your machine is stable otherwise (I dont have another game that can max all 4 cores of my q6600 and gets 100% on my 5850 at the same time), then fair enough, wait for the patch
That said, its been some time since I played Civ4. Beyond the Sword wasnt out, only Warlords. And no user mods.