IMHO, I like h.323 better. Primarily because it is easier to troubleshoot. The downside is that if you make changes, you have to consider the gateway also, so you are making changes to both CallManager and the gateway.
We had the same need to switch from H323 to MGCP in a remote site.
On the whole though both have worked very well for us. ON the new MGCP code (12.2.11T) there appears to be some documented bugs with ISDN line status not displaying on certain types of trunks including some or all types of PRI which is irritating - but i can live with it.
On the whole we've been pleased with MGCP - but then again outside of the dial peer maintenance which was a tremendous pain in the neck, we were never really displeased with H.323 either.
Are you getting this error “Installer User Interface Mode Not Supported. The installer cannot run in this UI mode. To specify the interface mode, use the -i command-line option, followed by the UI mode identifier. The value UI mode identifiers...
The below trick might come handy when you have to add a new node to a cluster but you don't have or is unsure of the security password for the publisher. This procedure has been around for ages.
1) Login into the CLI of the Publisher.