HELI ICE: use the search facility on this forum, there is a mountain of information available under "mountain flying"
Geronimo: I've done both, Trained in the Rockies and work in the lumps and bumps of the UK. It's the same as far as 'local weather' is concerned, you can't experience the whole mountain range at one go.
The principles are the same with both techniques and weather phenomena. Big isn't always better
Both can bite.
[I'm assuming aircraft performance isn't an issue. ]