If you bear the cost and take the pain to carry emergency equipment, and actually rely on it to have the freedom to do slightly foolish things, you'd better make sure it's going to work when needed.
A VHF is only useful if there is someone nearby listening (which isn't guaranteed) and who can speak your language. If you go trekking in the Himalayas, a VHF might be blocked by the mountains. It happened to us in Patagonia: two cops were trying to rescue a guy but they couldn't call for help because their radio wouldn't reach the nearest police station. Same thing in Bolivia when a guy crashed just in front of us in an area out of range for cell-phones. No such problem when we pulled out the sat-phone...
Just carrying a sat-phone isn't sufficient, though. You have to know who to call and be able to tell them where you are. At a minimum, enter the phone numbers of your embassies and consulates, and give them a buzz just to make sure the number is correct (in developing countries, phone numbers and area codes change rapidly). In really remote areas, it might help to talk to the local police station and take their number.
A sat-phone isn't just for far-away lands. I like to carry it too when I go alone on dirt roads in the western US (Nevada, Utah...), and I usually register with the local sheriff or ranger station. You can easily ride an entire day and not see anybody.
Pierre (& Merritt too)