The HF panels are thin film, which = less expensive + less efficient.
Si panels are typical for terrestrial flat panel applications now...but lots of new technology is being worked on. Problem for now is it's pretty expensive, but lots of new stuff including flexible solar cells (not the one's on the market now, but much higher in efficiency).
The new cells are expensive, so they use concentration on them...magnifying the suns power up to a few hundred times. This keeps the cost lower as the cell size is kept small for the amount of power produced.
Some companies are working on this new technology for consumer use, but it's still a few years out and will still be expensive for awhile.
I'd go with a good Si panel for now.
Homepower is a good magazine/site for good info on solar, wind and hydro power.
www.homepower.com