We've very much enjoyed Capella Ixtapa and are returning for New Year. The weather at the end of December is warmer than Cabo, quite perfect, in my opinion.
The plunge pools in Ixtapa are larger and more private than those in Cabo but the bathrooms don't have tubs. To make up for it, the showers have glorious ocean views.
The biggest issue with Ixtapa is getting there; it's not easy from much of anywhere. There are flights from LAX, PHX, IAH and once a week from DFW. None of this is daily.