I take the latter method, the buying points method. With Starwood and Hilton and LifeMiles and IHG, it's very straightforward because there is no difference between whether you use all points or C+P. However, with Hyatt I always include the amount that I'm willing to pay per elite night because C+P counts as elite night and point redemptions do not. I'm willing to generally pay about $20/stay (varies according to promos, of course), so I factor that in and will "pay" a little more to do C+P. I do very few paid stays with Hyatt.