Analysis paralysis on tripod purchase!!
I believe carbon is better at absorbing vibration than aluminium. Similar size tripods in carbon are noticeably lighter than aluminium. I have had the same Gitzo problems as mentioned in an earlier post. The top of the legs on mine are threaded so that they are both screwed and glued into the metal ferrule. Mine have come apart and I have now fixed them myself with epoxy glue. I also find the leg locks need careful tightening to prevent slipping. Giottos carbon tripods get a good name here in the UK, and are well priced. You should look at them if they are available where you are. I have a Manfrotto o55 in alu which is great, but I wouldn't carry it very far. Alex